Etymologies: Lycanthropy

Isidore

Legitur et de sacrificio quod Arcades deo suo Lycaeo immolabant, ex quo quicumque sumerent in bestiarum formas convertebantur.
And it is also said about the sacrifice which the Arcadians offered to their Lykaian god, that whosoever partook of them, they were changed into the forms of beasts.