Celts (or pronunciation, see Names of the Celts; the most common academic usage is with a hard, Latinic, "c", pronounced as "k"), is a modern term used to describe any of the European peoples who spoke, or speak, a Celtic language. The term is also used in a wider sense to describe the modern descendants of those peoples, notably those who participate in a Celtic culture.
The historical Celts were a diverse group of tribal societies in Iron Age Europe. Proto-Celtic culture formed in the Early Iron Age in Central Europe (Hallstatt period, named for the site in present-day Austria). By the later Iron Age (La Tène period), Celts had expanded over wide range of lands: as far west as Ireland and the Iberian Peninsula, as far east as Galatia (central Anatolia), and as far north as Scotland.
The earliest direct attestation of a Celtic language are the Lepontic inscriptions, beginning from the 6th century BC. Continental Celtic languages are attested only in inscriptions and place names. Insular Celtic is attested from about the 4th century AD in ogham inscriptions. Literary tradition begins with Old Irish from about the 8th century. Coherent texts of Early Irish literature, such as the Táin Bó Cúailnge, survive in 12th century recensions.
By the early centuries AD, following the expansion of the Roman Empire and the Great Migrations (Migration Period) of Germanic peoples, Celtic culture had become restricted to the British Isles (Insular Celtic), with the Continental Celtic languages extinct by the mid-1st millennium AD. "Celtic Europe" today refers to the lands surrounding the Irish Sea, as well as Cornwall and Brittany on either side of the English Channel.
The origin of the various names used since classical times for the people known today as the Celts is obscure and has been controversial. In particular, there are actually 19 records of the term 'pictish' being used in connection with the inhabitants of Ireland and Britain prior to the 18th century.
The Latin name Celtus (pl. Celti or Celtae; Greek Κέλτης pl. Κέλται or Κελτός pl. Κελτοί, Keltai or Keltoi) seems to be based on a native Celtic ethnic name. However, the first literary reference to the Celtic people, as Κελτοί (Κeltoi), is by the Greek historian Hecataeus of Miletus in 517 BC; he says that the town of Massilia (Marseille) is near the Celts and also mentions a Celtic town of Nyrex (possibly Noreia in Austria). Herodotus seems to locate the Keltoi at the source of the Danube and/or in Iberia, but the passage is unclear.
The English word Celt is modern, attested from 1707 in the writings of Edward Lhuyd whose work, along with that of other late 17th century scholars, brought academic attention to the languages and history of these early inhabitants of Great Britain.
Latin Gallus might originally be from a Celtic ethnic or tribal name, perhaps borrowed into Latin during the early 400s BC Celtic expansions into Italy. Its root may be the Common Celtic *galno, meaning 'power' or 'strength'. The Greek Galatai seems to be based on the same root, borrowed directly from the same hypothetical Celtic source which gave us Galli (the suffix -atai is simply an ethnic name indicator). (see Galatia in Anatolia)
The English form Gaul comes from the French Gaule and Gaulois, which is the traditional rendering of Latin Gallia and Gallus, -icus respectively. However, the diphthong au points to a different origin, namely a Romance adaptation of the Germanic *Walha-. (see Gaul: Name) The English word 'Welsh' originates from the word wælisc, the Anglo-Saxon form of walhiska-, the Germanic word for "foreign".
'Celticity' generally refers to the cultural commonalities of these peoples, based on similarities in language, material artifacts, social organisation and mythological factors. Earlier theories were that this indicated a common racial origin but more recent theories are reflective of culture and language rather than race. Celtic cultures seem to have had numerous diverse characteristics but the commonality between these diverse peoples was the use of a Celtic language.
'Celtic' is a descriptor of a family of languages and, more generally, means 'of the Celts,' or 'in the style of the Celts'. It has also been used to refer to several archaeological cultures defined by unique sets of artifacts. The link between language and artifact is aided by the presence of inscriptions. (see Celtic (disambiguation) for other applications of the term)
Today, the term 'Celtic' is generally used to describe the languages and respective cultures of Ireland, Scotland, Wales, Cornwall, the Isle of Man and Brittany, also known as the Six Celtic Nations. These are the regions where four Celtic languages are still spoken to some extent as mother tongues: Irish Gaelic, Scottish Gaelic, Welsh, and Breton plus two recent revivals, Cornish (one of the Brythonic languages) and Manx (one of the Goidelic languages). There are also attempts to revive the Cumbric language (a Brythonic language from Northwest England and Southwest Scotland). 'Celtic' is also sometimes used to describe regions of Continental Europe that have Celtic heritage, but where no Celtic language has survived; these areas include the western Iberian Peninsula, i.e. Portugal, and north-central Spain (Galicia, Asturias, Cantabria, Castile and León, Extremadura), and to a lesser degree, France. (see Modern Celts)
'Continental Celts' refers to the Celtic-speaking people of mainland Europe. 'Insular Celts' refers to the Celtic-speaking people of the British Isles and their descendants. The Celts of Brittany derive their language from migrating insular Celts from southwest Britain and so are grouped accordingly.
The Celtic languages form a branch of the larger Indo-European family. By the time speakers of Celtic languages enter history around 400 BC (Brennus's attack on Rome in 387 BC), they were already split into several language groups, and spread over much of Central Europe, the Iberian peninsula, Ireland and Britain.
Some scholars think that the Urnfield culture of northern Germany and the Netherlands represents an origin for the Celts as a distinct cultural branch of the Indo-European family. This culture was preeminent in central Europe during the late Bronze Age, from ca. 1200 BC until 700 BC, itself following the Unetice and Tumulus cultures. The Urnfield period saw a dramatic increase in population in the region, probably due to innovations in technology and agricultural practices. The Greek historian Ephoros of Cyme in Asia Minor, writing in the fourth century BC, believed that the Celts came from the islands off the mouth of the Rhine who were "driven from their homes by the frequency of wars and the violent rising of the sea".
The spread of iron-working led to the development of the Hallstatt culture directly from the Urnfield (c. 700 to 500 BC). Proto-Celtic, the latest common ancestor of all known Celtic languages, is considered by this school of thought to have been spoken at the time of the late Urnfield or early Hallstatt cultures, in the early first millennium BC. The spread of the Celtic languages to Iberia, Ireland and Britain would have occurred during the first half of the 1st millennium, the earliest chariot burials in Britain dating to ca. 500 BC. Over the centuries they developed into the separate Celtiberian, Goidelic and Brythonic languages.
The Hallstatt culture was succeeded by the La Tène culture of central Europe, and during the final stages of the Iron Age gradually transformed into the explicitly Celtic culture of early historical times. Celtic river-names are found in great numbers around the upper reaches of the Danube and Rhine, which led many Celtic scholars to place the ethnogenesis of the Celts in this area.
Diodorus Siculus and Strabo both suggest that the Celtic heartland was in southern France. The former says that the Gauls were to the north of the Celts but that the Romans referred to both as Gauls. Before the discoveries at Hallstatt and La Tene, it was generally considered that the Celtic heartland was southern France, see Encyclopedia Britannica for 1813.
Almagro-Gorbea proposed the origins of the Celts could be traced back to the third millennium BC, seeking the initial roots in the Bell Beaker culture, thus offering the wide dispersion of the Celts throughout western Europe, as well as the variability of the different Celtic peoples, and the existence of ancestral traditions an ancient perspective.
Traditionally the Celts were considered a Central European Iron Age phenomenon, through the cultures of Hallstatt and La Tène. However, archaeological finds from the Hallstatt and La Tène cultures were rare in the Iberian Peninsula, and did not provide enough evidence for a cultural scenario comparable to that of Central Europe. It is considered equally difficult to maintain that the origin of the Peninsular Celts can be linked to the preceding Urnfield culture, leading to a more recent approach that introduces a 'proto-Celtic' substratum and a process of Celticization having its initial roots in the Bronze Age Bell Beaker culture.
The Iron Age Hallstatt (c. 800-475 BC) and La Tène (c. 500-50 BC) cultures are typically associated with Proto-Celtic and Celtic culture. The La Tène culture developed and flourished during the late Iron Age (from 450 BCE to the Roman conquest in the 1st century BCE) in eastern France, Switzerland, Austria, southwest Germany, the Czech Republic, Slovakia and Hungary. It developed out of the Hallstatt culture without any definite cultural break, under the impetus of considerable Mediterranean influence from Greek, and later Etruscan civilizations. A shift of settlement centres took place in the 4th century.
The western La Tène culture corresponds to historical Celtic Gaul. Whether this means that the whole of La Tène culture can be attributed to a unified Celtic people is difficult to assess; archaeologists have repeatedly concluded that language, material culture, and political affiliation do not necessarily run parallel. Frey notes that in the 5th century, "burial customs in the Celtic world were not uniform; rather, localised groups had their own beliefs, which, in consequence, also gave rise to distinct artistic expressions". Thus, while the La Tène culture is certainly associated with the Gauls, the presence of La Tène artefacts may be due to cultural contact and does not imply the permanent presence of Celtic speakers.
At the dawn of history in Europe, the Celts then living in what is now France were known as Gauls to the Romans. The territory of these peoples probably included the low countries, the Alps and what is now northern Italy. Their descendants were described by Julius Caesar in his Gallic Wars. Eastern Gaul was the centre of the western La Tene culture. In later Iron Age Gaul, the social organization was similar to that of the Romans, with large towns. From the third century BC the Gauls adopted coinage, and texts with Greek characters are known in southern Gaul from the second century.
Greek traders founded Massalia in about 600BC, with exchange up the Rhone valley, but trade was disrupted soon after 500BC and re-oriented over the Alps to the Po valley in Italy. The Romans arrived in the Rhone valley in the second century BC and encountered a Gaul that was mostly Celtic-speaking. Rome needed land communications with its Iberian provinces and fought a major battle with the Saluvii at Entremont in 124-123 BC. Gradually Roman control extended, and the Roman Province of Gallia Transalpina was formed along the Mediterranean coast. The remainder was known as Gallia Comata - "Hairy Gaul".
In 58 BC, the Helvetii planned to migrate westward but were forced back by Julius Caesar. He then became involved in fighting the various tribes in Gaul, and by 55 BC, most of Gaul had been overrun. In 52 BC, Vercingetorix led a revolt against the Roman occupation but was defeated at the siege of Alesia and surrendered.
Following the Gallic Wars of 58-51 BC, Celticia formed the main part of Roman Gaul. Place name analysis shows that Celtic was used east of the Garonne river and south of the Seine and Marne.
Until the end of 19th century traditional scholarship surrounding the Celts acknowledged the celts of the Iberian Peninsula , as material culture relatable to the Hallstatt and La Tène cultures that since the XIX century defined Iron Age Celts was rare in Iberia, and did not provide a cultural scenario that could easily be linked to that of Central Europe the celts of the Iberian Peninsula became ignored until the end of the XX century. Three divisions, of the celts of the Iberian Peninsula, were made, the celtiberians in the mountains near the center of the peninsula,the celtici in the south west and the celts in the north west.
Modern scholarship, however, has proven that Celtic presence and influences were very substantial in Iberia. The Celts in Iberia were divided in two main archaeological and cultural groups, even if the divide is not very clear:
The origins of the Celtiberians might provide a key to unlocking the Celticization process in the rest of the Peninsula. The process of celticization of the southwest by the Keltoi and of the northwest is however not a simple celtiberian question. Recent investigation about the Callaici Bracari in northwest Portugal is bringing new approaches to understanding Celtic culture (language, art and religion) in western Iberia.
At the battle of Telemon in 225 BC a large Celtic army was trapped between two Roman forces and crushed.
The defeat of the combined Samnite, Celtic and Etruscan alliance by the Romans in the Third Samnite War sounded the beginning of the end of the Celtic domination in mainland Europe, but it was not until 192 BC that the Roman armies conquered the last remaining independent Celtic kingdoms in Italy.
The Celts settled much further south of the Po River than many maps show. Remnants in the town of Doccia, in the province of Emilia-Romagna, showcase Celtic houses in very good condition dating from about the 4th century BC.
Further south, Celts settled in Thrace (Bulgaria), which they ruled for over a century, and Anatolia, where they settled as the Galatians (see also: Gallic Invasion of Greece). Despite their geographical isolation from the rest of the Celtic world, the Galatians maintained their Celtic language for at least seven hundred years. St Jerome, who visited Ancyra (modern-day Ankara) in 373 AD, likened their language to that of the Treveri of northern Gaul.
The Boii tribe gave their name to Bohemia and Bologna, and Celtic artefacts and cemeteries have been discovered further east in what is now Poland and Slovakia. A celtic coin (Biatec) from Bratislava's mint is displayed on today's Slovak 5 crown coin.
As there is no archaeological evidence for large scale invasions in some of the other areas, one current school of thought holds that Celtic language and culture spread to those areas by contact rather than invasion. However, the Celtic invasions of Italy and the expedition in Greece and western Anatolia, are well documented in Greek and Latin history.
There are records of Celtic mercenaries in Egypt serving the Ptolemies. Thousands were employed in 283-246 BC and they were also in service around 186 BC. They attempted to overthrow Ptolemy II.
A large portion of the indigenous populations of Britain and Ireland today may be partially descended from the ancient peoples that have long inhabited these lands, before the coming of Celtic and later Germanic peoples, language and culture. Little is known of their original culture and language, but remnants of the latter may remain in the names of some geographical features, such as the rivers Clyde, Tamar and Thames, whose etymology is unclear but possibly derive from a pre-Celtic substrate (Gelling). By the Roman period, however, most of the inhabitants of the isles of Ireland and Britain were speaking Goidelic or Brythonic languages, close counterparts to the Celtic languages spoken on the European mainland.
Historians explained this as the result of successive invasions from the European continent by diverse Celtic-speaking peoples over the course of several centuries, though this is now generally seen as only the elite. The Book of Leinster, written in the twelfth century, but drawing on a much earlier Irish oral tradition, states that the first Celts to arrive in Ireland were from Iberia. In 1946 the Celtic scholar T. F. O'Rahilly published his extremely influential model of the early history of Ireland which postulated four separate waves of Celtic invaders. It is still not known what languages were spoken by the peoples of Ireland and Britain before the arrival of the Celts.
Later research indicated that the culture may have developed gradually and continuously between the Celts and the indigenous people of Britain or Spain. Similarly in Ireland little archaeological evidence was found for large intrusive groups of Celtic immigrants, suggesting to archaeologists such as Colin Renfrew that the native late Bronze Age inhabitants gradually absorbed European Celtic influences and language.
Julius Caesar wrote of people in Britain who came from Belgium (the Belgae), but archaeological evidence which was interpreted in the 1930s as confirming this was contradicted by later interpretations. The archaeological evidence is of substantial cultural continuity through the first millennium BC, although with a significant overlay of selectively-adopted elements of La Tène culture. There are claims of continental-style states appearing in southern England close to the end of the period, possibly reflecting in part immigration by élites from various Gallic states such as those of the Belgae. However, this immigration would be far too late to account for the origins of Insular Celtic languages. In the 1970s the continuity model was popularized by Colin Burgess in his book The Age of Stonehenge which theorised that Celtic culture in Great Britain "emerged" rather than resulted from invasion and that the Celts were not invading aliens, but the descendants of the people of Stonehenge.
Genetic studies have supported the prevalence of native populations, ruling out any model of post-Bronze Age cultural and language intrusion that ignore a very high degree of genetic absorpsion. A study by Christian Capelli, David Goldstein and others at University College, London showed that genes associated with Gaelic names in Ireland and Scotland are also common in certain parts of Wales and England (in most cases, The Southeast of England with the lowest counts of these genes) are similar to the genes of the Basque people, who speak a non-Indo-European language. This similarity supported earlier findings in suggesting a large pre-Celtic genetic ancestry, likely going back to the Paleolithic. They suggest that Celtic culture and the Celtic language may have been imported to Britain by cultural contact, not mass invasions around 600 BC.
Some recent studies have suggested that, contrary to long-standing beliefs, the Germanic tribes (Angles, Saxons) did not wipe out the Romano-British of England but rather, over the course of six centuries, conquered the native Brythonic people of what is now England and south-east Scotland and imposed their culture and language upon them, much as the Gaels may have spread over Northern Britain. The Pennines remained a stronghold for Brythonic culture in England, the Cumbric language survived until the 12th Century, whereas in isolated areas of East Anglia, a Brythonic language was only recorded as late as the Saxon period. Parts of the Brythonic culture still survives in the form of the Northumbrian smallpipes and Wrestling (Lancashire and Cumbrian wrestling). Still, others maintain that the picture is mixed and that in some places the indigenous population was indeed wiped out while in others it was assimilated. According to this school of thought the populations of Yorkshire, East Anglia, Northumberland and the Orkney and Shetland Islands are those populations with the fewest traces of ancient (Celtic) British continuation, probably because these are eastern areas which were exposed to invasion from the East by Angles, Saxons and Vikings.
The Celtic invasion of the British Isles is difficult to document genetically. Two published books - The Blood of the Isles by Bryan Sykes and The Origins of the British: a Genetic Detective Story by Stephen Oppenheimer - are based upon recent genetic studies, and show that the vast majority of Britons have ancestors from the Iberian Peninsula, as a result of a series of migrations that took place during the Mesolithic and, to a lesser extent, the Neolithic eras.
Sykes sees little genetic evidence relating to people from the heartland of the Hallstatt and La Tene cultures. On the paternal side he finds that the "Oisin" (R1b) clan is in the majority which has strong affinities to Iberia, with no evidence of a large scale arrival from Central Europe. He considers that the genetic structure of Britain and Ireland is "Celtic":
Evidence for Celts in England can be found in place names, such as those including the Old English element, 'wahl', meaning 'foreigner' or 'stranger'. A smattering of villages around the Fenland town of Wisbech hint at this. West Walton, Walsoken, and the Walpoles indicate the continued presence of an indigenous population, and Wisbech, King's Lynn and Chatteris retain proto-Celtic topographical elements. Villages which exhibit Tydd in their name, eg Tydd St. Giles may obtain that element from the Brythonic word for "small holding". Compare the Welsh "tyddyn". Saxon Etheldreda's 'Liber Eliensis' documents the Fenland tribe of the Girvii (Gywre), who are cited elsewhere as being an independent people with dark hair and their own (Brythonic?) language. It is entirely possible that the Girvii were formed in part by migrating Britons, displaced by Saxon settlers after the legions left the Isles.
The native peoples under Roman rule became Romanized and keen to adopt Roman ways. Celtic art had already incorporated classical influences, and surviving Gallo-Roman pieces interpret classical subjects or keep faith with old traditions despite a Roman overlay.
The Roman occupation of Gaul, and to a lesser extent of Britain, led to Roman-Celtic syncretism (see Roman Gaul, Roman Britain). In the case of the continental Celts, this eventually resulted in a language shift to Vulgar Latin (see also Gallo-Roman culture), while the Insular Celts retained their language. However, the Celts were master horsemen, which so impressed the Romans that they adopted Epona, the Celtic horse goddess, into their pantheon. During and after the fall of the Roman Empire many parts of France threw out their Roman administrators.
The French archaeologist J. Monard speculated that it was recorded by druids wishing to preserve their tradition of timekeeping in a time when the Julian calendar was imposed throughout the Roman Empire. However, the general form of the calendar suggests the public peg calendars (or parapegmata) found throughout the Greek and Roman world
There were four major festivals in the Gallic Calendar: "Imbolc" on 1 February, possibly linked to the lactation of the ewes and sacred to the Irish Goddess Brigid. "Beltaine" on 1 May, connected to fertility and warmth, possibly linked to the Sun God Belenos. "Lúnasa" on 1 August, connected with the harvest and associated with the God Lugh. And finally "Samhain" on 1 November, possibly the start of the year. Two of these festivals, Beltaine and Lúnasa are shown on the Coligny Calendar by sigils, and it is not too much of a stretch of the imagination to match the first month on the Calendar (Samonios) to Samhain. Imbolc does not seem to be shown at all however.
The Celtic Calendar seems to be based on astronomy but how any astrology system would have worked is harder to tell. We have to base our knowledge on Old Irish manuscripts, none of which have been published or fully translated. It seems to have been based on an indigenous Irish symbol system, and not that of any of the more commonly-known astrological systems such as Western, Chinese or Vedic astrology.
In the main, the evidence is of tribes being led by kings, although some argue that there is evidence of oligarchical republican forms of government eventually emerging in areas in close contact with Rome. Most descriptions of Celtic societies describe them as being divided into three groups: a warrior aristocracy; an intellectual class including professions such as druid, poet, and jurist; and everyone else. There are instances recorded where women participated both in warfare and in kingship, although they were in the minority in these areas. In historical times, the offices of high and low kings in Ireland and Scotland were filled by election under the system of tanistry, which eventually came into conflict with the feudal principle of primogeniture where the succession goes to the first born son.
Little is known of family structure among the Celts. Athenaeus in his Deipnosophists, 13.603, claims that "the Celts, in spite of the fact that their women are the most beautiful of all the barbarian tribes, prefer boys as sexual partners. There are some of them who will regularly go to bed – on those animal skins of theirs – with a pair of lovers", implying a woman and a boy. Such reports reflect an outsider's observation of Celtic culture. It is unknown whether Athenaeus, born in Egypt of Greek origin ever visited any Celts since little is known about him beyond his surviving writings.
Patterns of settlement varied from decentralised to the urban. The popular stereotype of non-urbanised societies settled in hillforts and duns, drawn from Britain and Ireland contrasts with the urban settlements present in the core Hallstatt and La Tene areas, with the many significant oppida of Gaul late in the first millennium BC, and with the towns of Gallia Cisalpina.
There is archaeological evidence to suggest that the pre-Roman Celtic societies were linked to the network of overland trade routes that spanned Eurasia. Large prehistoric trackways crossing bogs in Ireland and Germany have been found by archaeologists. They are believed to have been created for wheeled transport as part of an extensive roadway system that facilitated trade. The territory held by the Celts contained tin, lead, iron, silver and gold. Celtic smiths and metalworkers created weapons and jewelry for international trade, particularly with the Romans.
Local trade was largely in the form of barter, but as with most tribal societies they probably had a reciprocal economy in which goods and other services are not exchanged, but are given on the basis of mutual relationships and the obligations of kinship. Low value coinages of potin, silver and bronze, suitable for use in trade, were minted in most Celtic areas of the continent, and in South-East Britain prior to the Roman conquest of these areas.
There are only very limited records from pre-Christian times written in Celtic languages. These are mostly inscriptions in the Roman, and sometimes Greek, alphabets. The Ogham script was mostly used in early Christian times in Ireland and Scotland (but also in Wales and England), and was only used for ceremonial purposes such as inscriptions on gravestones. The available evidence is of a strong oral tradition, such as that preserved by bards in Ireland, and eventually recorded by monasteries. The oldest recorded rhyming poetry in the world is of Irish origin and is a transcription of a much older epic poem, leading some scholars to claim that the Celts invented Rhyme. They were highly skilled in visual arts and Celtic art produced a great deal of intricate and beautiful metalwork, examples of which have been preserved by their distinctive burial rites.
In some regards the Atlantic Celts were conservative, for example they still used chariots in combat long after they had been reduced to ceremonial roles by the Greeks and Romans, though when faced with the Romans in Britain, their chariot tactics defeated the invasion attempted by Julius Caesar.
According to Diodorus Siculus:
Under Brehon Law, which was written down in early Medieval Ireland after conversion to Christianity, a woman had the right to divorce her husband and gain his property if he was unable to perform his maritial duties due to impotence, obesity, homosexual inclination or preference for other women.
Very few reliable sources exist regarding Celtic views towards gender divisions, though some archaeological evidence does suggest that their views towards gender roles may have been different from those of their contemporary classical counterparts. There are instances recorded where women participated both in warfare and in kingship, although they were in the minority in these areas. Plutarch reports Celtic women acting as ambassadors to avoid a war amongst Celts chiefdoms on the Po valley during the 4th century BC.
There are some general indications coming from Iron Age burial sites in the Champagne and Bourgogne regions of Northeastern France suggesting that women may have had roles in combat during the earlier portions of the La Tène period. The evidence is, however, far from conclusive. Examples of individuals buried with both torcs (generally associated as being female grave goods), and weaponry have been identified, and there are some questions regarding the sexing of some skeletons that were buried with warrior assemblages.
Among the insular Celts, there is a greater amount of historic documentation to suggest warrior roles for women however. In addition to commentary by Tacitus about Boudica, there are indications from later period histories that also suggest a more substantial role for "women as warriors" in symbolic if not actual roles.
Posidonius and Strabo described an island of women where men could not venture to for fear of death and the women ripped each other apart. Other writers, such as Ammianus Marcellinus and Tacitus, mentioned Celtic women inciting, participating, and leading battles. Poseidonius' anthropological comments on the Celts had common themes, primarily primitivism, extreme ferocity, cruel sacrificial practices, and the strength and courage of their women.
The Celts were described by classical writers such as Strabo, Livy, Pausanias, and Florus as fighting like "wild beasts", and as hordes. Dionysius said that their "manner of fighting, being in large measure that of wild beasts and frenzied, was an erratic procedure, quite lacking in military science. Thus, at one moment they would raise their swords aloft and smite after the manner of wild boars, throwing the whole weight of their bodies into the blow like hewers of wood or men digging with mattocks, and again they would deliver crosswise blows aimed at no target, as if they intended to cut to pieces the entire bodies of their adversaries, protective armour and all". Such descriptions have been challenged by contemporary historians.
A further example of this regeneration after beheading lies in the tales of Connemara's St. Feichin, who after being beheaded by Viking pirates carried his head to the Holy Well on Omey Island and on dipping the head into the well placed it back upon his neck and was restored to full health.
Diodorus Siculus, in his 1st century History had this to say about Celtic head-hunting:
In Gods and Fighting Men, a translation of early Irish mythology by prominent Irish translator Lady Gregory, heads of men killed in battle are described in the beginning of the story The Fight With The Fir Bolgs as pleasing to Macha, one aspect of the Morrigu (the Irish trinity of war-goddesses).
The Celts believed that if they attached the head of their enemy to a pole or a fence near their house, the head would start screaming when the enemy was near. The Celtic headhunters venerated the image of the severed head as a continuing source of spiritual power. If the head is the seat of the soul, possessing the severed head of an enemy, honorably reaped in battle, added prestige to any warrior's reputation. According to tradition the buried head of a god or hero named Bran the Blessed protected Britain from invasion across the English Channel. However, the Celts only took heads of those which they deemed to be worthy of respect, and did not go to battle seeking to take them, so 'head hunters' is probably inaccurate
Many Celtic gods are known from texts and inscriptions from the Roman period, such as Aquae Sulis, while others have been inferred from place names such as Lugdunum (stronghold of Lug). Rites and sacrifices were carried out by priests, some known as Druids. The Celts did not see their gods as having a human shape until late in the Iron Age. Celtic shrines were situated in remote areas such as hilltops, groves, and lakes.
Celtic religious patterns were regionally variable, however some patterns of deity forms, and ways of worshiping these deities, appear over a wide geographical and temporal range. The Celts worshipped both gods and goddesses. In general, the gods were deities of particular skills, such as the many-skilled Lugh and Dagda, and the goddesses associated with natural features, most particularly rivers, such as Boann, goddess of the River Boyne. This was not universal, however, as Goddesses such as Brighid and The Morrígan were associated with both natural features (holy wells and the River Unius) and skills such as blacksmithing, healing, and warfare.
Triplicities are a common theme in Celtic cosmology and a number of deities were seen as threefold.
The Celts had literally hundreds of deities, some unknown outside of a single family or tribe, while others were popular enough to have a following that crossed boundaries of language and culture. For instance, the Irish god Lugh, associated with storms, lightning, and culture, is seen in a similar form as Lugos in Gaul and Lleu in Wales. Similar patterns are also seen with the continental Celtic horse goddess Epona, and what may well be her Irish and Welsh counterparts, Macha and Rhiannon, respectively.
Roman reports of the druids mention ceremonies being held in sacred groves. La Tène Celts built temples of varying size and shape, though they also maintained shrines at sacred trees, and votive pools.
Druids fulfilled a variety of roles in Celtic religion, as priests and religious officiants, but also as judges, sacrificers, teachers, and lore-keepers. In general, they were the "college professors" of their time. Druids organized and ran the religious ceremonies, as well as memorizing and teaching the calendar. Though generally quite accurate, the Celtic calendar required manual correction about every 40 years, therefore knowledge of mathematics was required. Other classes of druids performed ceremonial sacrifices of crops and animals for the perceived benefit of the community.
While the regions under Roman rule adopted Christianity along with the rest of the Roman empire, unconquered areas of Ireland and Scotland moved from Celtic polytheism to Celtic Christianity in the fifth century AD. Ireland was converted under missionaries from Britain such as Patrick. Later missionaries from Ireland were a major source of missionary work in Scotland, Saxon parts of Britain and central Europe (see Hiberno-Scottish mission). This brought the early medieval renaissance of Celtic art between 390 and 1200 A.D., developing many of the styles now thought of as typically Celtic, and found through much of Ireland and Britain, including the north-east and far north of Scotland, Orkney and Shetland. This was brought to an end by Roman Catholic and Norman influence, though the Celtic languages, as well as some and some influences from Celtic art, continued.
The development of Christianity in Ireland and Britain brought an early medieval renaissance of Celtic art between 400 and 1200, only ended by the Norman Conquest of Ireland in the late 12th century. Notable works produced during this period include the Book of Kells and the Ardagh Chalice. Antiquarian interest from the 17th century led to the term 'Celt' being extended, and rising nationalism brought Celtic revivals from the 19th century.