The aim of this paper is twofold. Firstly, a case will be made for the Old Norse myth of Thjalfi’s laming of Thor’s goat (chiefly attested in Gylfaginning 44) as a Scandinavian counterpart to two Ancient Greek myths, the myth of Hermes’s theft of Apollo’s cows (and slaughter of two of them), most extensively attested in the Homeric Hymn to Hermes, and the myth of Prometheus’s (attempted) deception of Zeus during the slaughter of a cow at Mekone, attested in Hesiod’s Theogony, whose several correspondences allow for the reconstruction of an ancient Indo-European tradition in which the aetiology of a ritual was connected with a mythological incident involving livestock. Secondly, an attempt will be made to reconstruct the corresponding ritual with the aid of insights from prehistoric archaeology.