In his claim of ‘authenticity’ for Old Norse mythology, the pioneering nineteenth-century scholar Jacob Grimm states a profoundly held belief that Old Norse mythological sources can give an accurate picture of what Norse heathenism was really like. He then argues that all the pre-Christian Germanic peoples shared a common poetic, religious and mythological tradition that was grounded in the natural world. He seeks to prove the antiquity of this system by demonstrating linguistic links with other Indo- European languages. For example, the Old Norse god-name Týr has the same root as Sanskrit Dyaus, Greek Zeus and Latin Jovis and divus. Similarly, later scholars pointed out the correspondence between Old Norse Ymir, the primeval giant from whose body-parts the cosmos was created, and the Iranian Yima and Sanskrit Yama. These names are taken to mean ‘twin’ (cf. Latin geminus), and related to Tuisto, the first ancestor of the Germani in Tacitus's Germania, and to the myth told in Vafþrúðnismál 33, where a boy and girl grow together under Aurgelmir's arm, while one of his legs begets a six-headed giant on the other. Snorri states that Aurgelmir is identical with Ymir (Gylfaginning ch. 5), though we do not know whether this is based on a lost source, or is merely his own assumption.

But these philological facts are hardly evidence for a common Indo- European religion. Since the Indo-European languages are related, it is not surprising that they share a root meaning ‘a divine being’. It does not follow that Dyaus, Zeus, Jovis and Týr are ‘the same god’, whatever that might mean. Admittedly, the Norse creation myth of Ymir shows some resemblance to some Iranian ones: in Gylfaginning ch. 6, Ymir is nourished by the milk of the cow Auðhumla, while the ancestor of all animals and plants in Zoroastrian mythology is the uniquely created bull.