The cognate term in Old English is ōs , denoting a god in Anglo-Saxon paganism. The Latinised Gothic term used by Jordanes is anses. They continue the hypothetical Proto-Germanic *ansuz form. The a-rune was named after the æsir. Unlike Old English god (and Old Norse goð), the term ōs (áss) was never adopted into Christian use.
The feminine is ás-ynja (plural ásynjur). The feminine -ynja suffix is known from a few other nouns denoting female animals, such as apynja "simia", vargynja "lupa". The word for "goddess" is not attested outside of Old Norse, but since the -ynja suffix is cognate to Old High German -inna (Modern German -in), an Old High German *ansinna has been reconstructed, from a Proto-Germanic *ansunja.
The latinization of Danish Aslak as Ansleicus indicates that the nasalization in the first syllable persisted into the 9th century.
The cognate Old English form to áss is ōs, preserved only as a prefix Ōs- in personal names, and as the genitive plural ēsa (ēsa gescot and ylfa gescot, "the shots of anses and of elves", jaculum divorum et geniorum). Jordanes has anses for the gods of the Goths. The Proto-Germanic word was *ansu-z, with a plural *ansiwiz. The (reconstructed) Old High German terms given by Grimm are ans, plural anseis, ensî. Old Saxon ôs, plural ês''.
Grimm's Deutsches Wörterbuch under Ans (plural Ens) lists a noun meaning tignum, jugum ("stave, yoke"), in Bavarian and Tyrolian dialect denoting barrel staves, cognate to Gothic ans for δοκος "beam" and Old Norse áss "pole, beam, mountain-ridge". Grimm considers this word etymologically identical to áss "god", as he explains in his Deutsche Mythologie:
whether because the mighty gods were thought of as joist, rafter and ceiling of the sky, or that the notions of jugum and mountain-ridge were associated with them, for âs is especially used of jugum terræ, mountain-ridgeAnderson in his translation of the Prose Edda (1897) similarly states that "in this latter sense, the gods are the pillars of the universe," and notes that the sense "mountain-ridge" of ás had been compared to Strabo's Aspargum in the Caucasus (as "the Asburg or castle of the asas") "by those who look for historical fact in mythological tales". Grimm further notes a resemblance the name of the gods of the Etruscans reported by Suetonius and Hesychius, æsares or æsi.
The unification theories of the 1800s were reflected in conjectural discussions on the status of various Indo-Iranian entities that in Vedic Sanskrit were asuras and in Avestan were ahuras. Both words derive from Indo-Iranian *ásura, with the root *n̥su- reflecting "life" or "existence", especially existence in the other world. In turn, Indo-Iranian *n̥su- can be considered a zero-grade equivalent of Germanic *ansuz-, and with it could be reconstructed to derive from Proto-Indo-European *h2ensu-.
Today it is assumed that Indo-Iranian *Asura was originally the proper name of a specific divinity, and that the terms asura and ahura came to be subsequently used as an epithet of those divinities who were—in the nature of Indo-Iranian religious poetry—associated with the invoked entity and thus invoked along with it. Notwithstanding a possible etymological relationship with Germanic *ansuz-, the supposed points of comparison with figures from Norse mythology are demonstratively contrived; involving aspects of present-day Hinduism that were not features of Vedic religion, and so cannot be part of a continuing inheritance from Indo-Iranian—or even more remotely, Indo-European—times.
Other names considered to be etymologically related to Æsir include Greek Eos, Roman Aurora, Vedic Ushas, Lithuanian Aušra, Latvian Auseklis, Hittite assu, Gallic Esus, Slavic Iaro, and Albanian Arap Ushas. More remotely, Anatolian Estan, Greek Hestia, Roman Vesta, Armenian Astghik, Germanic Eostre, and Baltic Austija. These words do not, however, refer to a pantheon as they do in Germanic polytheism.
An áss like Ullr is almost unknown in the myths, but his name is seen in a lot of geographical names, especially in Sweden, and may also appear on the 3rd century Thorsberg chape, suggesting that his cult was widespread in prehistoric times.
In the Eddas, however, the word Æsir is used to call gods in general, while Asynjur is used to call the goddesses in general. For example, in the poem Skírnismál, Freyr was called "Prince of the Æsir". In the Prose Edda, Njord was introduced as "the third among the Æsir", and among the Asynjur, Freyja is always listed second only to Frigg.
In surviving tales, origin of many of the Æsir are doubtful and unexplained. Originally, there are just three: Odin and his brothers Ve, and Vili. Odin's sons with giantesses are naturally counted as Æsir. Heimdall and Ullr's connection with the Æsir is not clearly mentioned. Loki is a giant with no evidences of being worshipped, and Njord is a Vanir hostage, but they are often ranked among the Æsir.
Given the difference between their roles/emphases, some scholars have speculated that the interactions between the Aesir and the Vanir reflect the types of interaction the were occurring between social classes (or clans) within Norse society at the time. According to another theory, the Vanir (and the fertility cult associated with them) may be more archaic than that of the more warlike Aesir, such that the mythical war may mirror a half-remembered religious conflict. Another historical perspective is that the inter-pantheon interaction may be an apotheosization of the conflict between the Romans and the Sabines. Finally, the noted comparative religion scholar Mircea Eliade speculated this conflict is actually a later version of an Indo-European myth concerning the conflict between and eventual integration of a pantheon of sky/warrior/ruler gods and a pantheon of earth/economics/fertility gods, with no strict historical antecedents.
The name of a in the Gothic alphabet is ahsa. The common Germanic name of the rune may thus have either been ansuz "God, one of the Æsir", or ahsam "ear (of corn)"
As occurs in many Scandinavian names: Asbjørn, Asgeir (Asger, Asker), Asmund, Astrid, Asdîs, Asgautr, Aslaug, Åse etc. Gothic has Ansila, and Old High German Anso, Anshelm, Anshilt, Anspald, Ansnôt.
In spite of the literal meaning of Ásatrú, most adherents do not emphasize worship of the Æsir in particular. The Íslenska Ásatrúarfélagið describes Ásatrú as "Nordic pantheism" involving "belief in the Icelandic/Nordic folklore" including all the "spirits and entities" besides "gods and other beings" this entails. Even more detached from historical Viking Age polytheism, The American Asatru Folk Assembly defines Ásatrú as "an expression of the native, pre-Christian spirituality of Europe" postulating it as "native European religion" in general "just as there is Native American religion and native African religion".