The original noun from which this adjective was produced has not been determined with confidence. The stem is theorized to have had the form *Ang?l/r-. The more prominent etymological theories concerning the name's origin have included:
Pope Gregory the Great is the first known to have simplified Anglii to Angli, which he did in an epistle, the latter form developing into the preferred form of the word in Britain and throughout the continent, (the generic form becoming Anglus in answer). The country remained Anglia in Latin. Meanwhile, there are several likenesses of form and meaning attested in Old English literature: King Alfred's (Alfred the Great) translation of Orosius uses Angelcynn (-kin) to describe England and the English people; Bede, Angelfolc (-folk); there are also such forms as Engel, Englan (the people), Englaland and Englisc, all showing signs of vocalic mutation and later developing into the dominant forms.
Strabo's mention of the Battle of Teutoburg Forest places his knowledge in the final years of Augustus' reign and after, which is the early first century. Strabo (7.2.1, 4 and 7.3.1) states that the Cimbri still live on the peninsula (Jutland) where they always did, even though some of them liked to wander. Beyond the Elbe the coastal people are unknown, but south of them are the Suebi from the Elbe to the Getae (Goths). Strabo worked eastward from the Rhine.
Pliny on the other hand worked from east to west (4.13.94). His description leaves the Black Sea, crosses the Ripaei mountains to the shore of the northern ocean, and follows it westward to Cadiz. In the first direction is direction in Scythia, where the Sarmati, Venedi, Sciri and Hirri are located, as far as the Vistula. Then the Inguaeones begin. Baunonia (Bornholm) is an island opposite Scythia. Cylipenus, probably the Bay of Kiel, is described, and from there a gulf called Lagnus, which is on the frontier of the Cimbri. Its location is not known, but it was likely in the Angeln region.
In Pliny, the Inguaeones consisted of the Cimbri and the Teutones (the Chauci as well, but they were not in this region). If Lagnus was situated on the Cimbrian frontier and after Kiel, then Angeln must have been in the territory of the Teutones. They were perhaps not named Angles at that time; however, the territory of the Teutones probably included the Vorpommern and the region south to the Elbe (mainly Holstein), accounting for the implied larger range of the people called Angles in later sources.
Possibly the first instance of the Angles in recorded history is in Tacitus' Germania, chapter 40, in which the Anglii are mentioned in passing in a list of Germanic tribes. He gives no precise indication of their geographical position but states that, together with six other tribes, they worshipped a goddess named Nerthus, whose sanctuary was situated on "an island in the Ocean." The other tribes are the Reudigni, Aviones, Varini, Eudoses, Suarini and Nuitones, which are together described as being behind ramparts of rivers and woods; that is, inaccessible to attack. As the Eudoses are the Jutes, these names probably refer to localities in Jutland or the Baltic coast; i.e., they are all Cimbri or Teutones. The coast contains sufficient estuaries, inlets, rivers, islands, swamps and marshes to have been then inaccessible to those not familiar with the terrain, such as the Romans, who labelled it unknown and inaccessible country.
The majority of scholars believe that the Anglii had lived from the beginning on the coasts of the Baltic Sea, probably in the southern part of the Jutish peninsula. The evidence for this view is derived partly from English and Danish traditions dealing with persons and events of the 4th century, and partly from the fact that striking affinities to the cult of Nerthus as described by Tacitus are to be found in Scandinavian, especially Swedish and Danish, religion.
Investigations in this subject have rendered it very probable that the island of Nerthus was Sjælland (Zealand), and the kings of Wessex traced their ancestry ultimately to a certain Scyld, who is clearly to be identified with Skiöldr, the mythical founder of the Danish royal family (Skiöldungar). In English tradition this person is connected with "Scedeland" (pl.), i.e. Scandinavia, while in Scandinavian tradition he is associated with the ancient royal residence at Lejre in Sjælland.
The account in Germania is contradictory to that of Strabo and Pliny in at least one major point. Tacitus viewed the Baltic as the Suebian Sea and lists the seven tribes as being in Suebian territory. The Suebi were among the Herminones of central Germany. And yet Pliny accounts for the Teutones as being Inguaeones, the Ingaevones of Tacitus. In Strabo, the Suebi are to the south of the coast. The Suebian language went on to become Old High German, while the Angles and Jutes were among the speakers of Old Saxon.
The Angles, as such, are not listed at all. Instead there are Syeboi Angeilloi , Latinized to Suevi Angili, located south of the middle Elbe. Owing to the uncertainty of this passage, there has been much speculation regarding the original home of the Angli. One theory is that they dwelt in the basin of the Saale (in the neighbourhood of the canton Engilin), from which region the Lex Angliorum et Werinorum hoc est Thuringorum is believed by many to have come.
A second possible solution is that these Angles of Ptolemy are not those of Schleswig at all. According to Julius Pokorny the Angri- in Angrivarii, the -angr in Hardanger and the Angl- in Anglii all come from the same root meaning "bend", but in different senses. In other words, the similarity of the names is strictly coincidental and does not reflect any ethnic unity beyond Germanic. The Suevi Angeli would have been in Lower Saxony or near it and, like Ptolemy's Suevi Semnones, were among the Suebi at the time.
Bede states that the Angli, before they came to Great Britain, dwelt in a land called Angulus, and similar evidence is given by the Historia Brittonum. King Alfred the Great and the chronicler Æthelweard identified this place with the district that is now called Angeln, in the province of Schleswig (Slesvig), though it may then have been of greater extent, and this identification agrees with the indications given by Bede. Confirmation is afforded by English and Danish traditions relating to two kings named Wermund and Offa, from whom the Mercian royal family were descended and whose exploits are connected with Angeln, Schleswig and Rendsburg. Danish tradition has preserved record of two governors of Schleswig, father and son, in their service, Frowinus (Freawine) and Wigo (Wig), from whom the royal family of Wessex claimed descent. During the 5th century the Angli invaded Great Britain, after which time their name does not recur on the continent except in the title of Suevi Angili.
The province of Schleswig has proved rich in prehistoric antiquities that date apparently from the 4th and 5th centuries A.D. A large cremation cemetery has been found at Borgstedterfeld, between Rendsburg and Eckernförde, which has yielded many urns and brooches closely resembling those found in heathen graves in England. Of still greater importance are the great deposits at Thorsberg moor (in Angeln) and Nydam, which contained large quantities of arms, ornaments, articles of clothing, agricultural implements, etc., and in the latter case even ships. By the help of these discoveries, Angle civilization in the age preceding the invasion of Great Britain can be pieced together.
According to sources such as the Bede, after the invasion of England, the Angles split up and founded the kingdoms of the Nord Angelnen (Northumbria), Ost Angelnen (East Anglia), and the Mittlere Angelnen (Mercia). Thanks to the major influence of the Saxons, the tribes were collectively called Anglo-Saxons by the Normans. The regions of East Anglia and Northumbria are still known by their original titles to this day. Northumbria once stretched as far north as south east Scotland, including Edinburgh.
The rest of that people stayed at the centre of the Angle homeland in the northeastern portion of the modern German bundesland of Schleswig-Holstein, on the Jutland Peninsula. There, a small peninsular form is still called "Angeln" today and is formed as a triangle drawn roughly from modern Flensburg on the Flensburger Fjord to the City of Schleswig and then to Maasholm, on the Schlei inlet.