Aesir-Asura correspondence is the relation between æsir, an Old Norse word meaning "gods" (the plural of the singular word áss "god") and ásuraḥ, a Sanskrit word referring to certain warlike and aggressive demons. Also related is the Avestan word ahura, found as the title of the god Ahura Mazda.
The Proto-Germanic form of Old Norse áss, deduced by comparison to other Germanic languages, living and dead, is *ansuz. The plural of this Proto-Germanic word was *ansiwiz, which by regular sound changes into æsir.
The word ásuraḥ can be postulated to come from Proto-Indo-Iranian *n̩suras, where *n̩su- is the zero-grade form equivalent to the Gemanic *ansu-, both from a Proto-Indo-European root *H2ensu-. In Sanskrit, ásuḥ (PIIr *n̩sus) means "vital spirit" or "life", and is presumably related, suggesting a common meaning "spirit".
Both words describe a family of divine beings, the Æsir is the pantheon of the principal Norse gods, and Asuras are a group of Hindu demons. Each group is set up against another group of gods; the Æsir warred with the Vanir, whereas the Asuras oppose the devas. In Norse mythology the Æsir are generally approved of (and worshipped) while the asuras have a more negative reputation in the Indian religions. However, the use of ahura to refer to the greatest god of Zoroastrianism implies that the word once had more favorable connotations.
The relationship between the Æsir and Vanir parallel the Asuras and Devas in another way; like the Æsir, the Asuras were associated in Vedic myth with human phenomena (contracts, the arts, fate), while the Vanir, like the Devas, are associated with the natural world (such as Njord and Freyr, associated with fertility).
Probable ancient oral history
It is not uncommon for migrational accounts to be found in early mythological and religious texts, a classical example being the Book of Exodus in the Torah, describing the legendary migration of the Israelites from Egypt to Canaan. In case of the Aesir-Asura correspondence, it could have been that the Indo-Iranian Asura or Ahura left India and traveled west until they found the home of the Vanir (and fought and defeated them). This be a very old story of human migration.
In the Indian stories, the violent Asura fight the Deva (Iranian Daeva) and leave. In Norse stories the Aesir arrive and fight with the more peaceable Vanir. When the Aesir win, they take hostages from the Vanir in the form of the god Nord, as well as his children Frey and Freja. It could be that the stories told in both places are related, that it tells the story of migration, perhaps the leaving of more aggressive members of the Indo-Iranian community, who then moved to the harsher climate of Europe and Scandinavia, bringing their own version of events with them.
- Watkins, Calvert. 2000. The American Heritage Dictionary of Indo-European Roots. New York, Houghton Mifflin.