lycanthropy (n.)

1580s, a form of madness (described by ancient writers) in which the afflicted thought he was a wolf, from Greek lykanthropia, from lykanthropos "wolf-man," from lykos "wolf" (see wolf (n.)) + anthrōpos "man" (from PIE root *ner- (2) "man"). Applied to actual transformations of persons (especially witches) into wolves since 1830 (see werewolf).