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 deities. 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. In the earlier Vedic literature also those we know of as Devas, like Indra, are called Asuras.
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 natural phenomena (such as Njord and Freyr, associated with fertility).
- Watkins, Calvert. 2000. The American Heritage Dictionary of Indo-European Roots. New York, Houghton Mifflin.