Ásatrú

Ásatrú, Ásatrumenn, Ásatruar, n. ("ow suh trew"): a New Age system of religious practice based loosely and spuriously upon pre-Christian Norse, Teutonic, and Anglo-Saxon paganism, particularly as described in medieval Icelandic Eddic literature; from Old Norse (áss "pagan war god" (pl. Æsir) + troth "loyalty"), c. 1970; pl. Ásatruar. [GJ1]
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Addendum #1: Ásatrú as a New Age movement was founded in the 1970s by Icelanders, called Ásatrumenn, seeking to reclaim their ethnic heritage. It was picked up by New Agers in Vinland (the U.S.) shortly thereafter. [GJ1].
Addendum #2: Gamers interested in Norse polytheism should check out the Get of Fenris rules and background materials in Werewolf: The Apocalypse. They should ignore anything in Marvel Comics' The Mighty Thor. If you're new to Norse Mythology, the best place to start is Norse Myths by Kevin Crossley-Holland.[GJ1]