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Name Proto-Germanic Anglo-Saxon Old Norse *Ansuz Ós; Ác; Æsc Óss "god" "god"; "oak"; "ash" "god" Shape Elder Futhark Futhorc Younger Futhark Unicode ᚨ U+16A8 ᚩ ᚪ ᚫ U+16A9 U+16AA U+16AB ᚬ U+16AC ᚭ U+16AD Transliteration a o; a; æ o Transcription a o; a; æ ą, o IPA [a(ː)] [o(ː)]; [ɑ(ː)]; [æ(ː)] [ɑ̃], [o(ː)] Position in rune-row 4 4; 25; 26 4

Variations of the rune in Younger Futhark.

The a-rune ᚨ, Younger Futhark ᚬ was probably named after the Æsir, in Proto-Germanic *Ansuz.

The shape of the rune is likely from Neo-Etruscan a (), like Latin A ultimately from Phoenician Aleph.

Its name survives only in the Icelandic rune poem as Óss, however, referring to Odin, identified with Jupiter:

ᚬÓss er algingautr

ok ásgarðs jöfurr,

ok valhallar vísi.

Jupiter oddviti.

Óss is aged Gautr

and prince of Ásgardr

and lord of Vallhalla.

chief Jupiter

The Norwegian rune poem, Óss has a meaning of "estuary" while in the Anglo-Saxon one, futhorc Os ᚩ has the Latin meaning of "mouth". The Younger Futhark rune is transliterated as ą to distinguish it from the new Ár rune (ᛅ), which continues the Jēran rune after loss of prevocalic *j- in Proto-Norse *jár (Old Saxon jār).

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)".

A variant of the rune is Futhorc Æsc ᚫ "ash". The Latin ligature Æ in Old English was called Æsc after the rune. Another variant is Ac "oak" ᚪ.