lycanthrope 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).

late Old English werewulf "person with the power to turn into a wolf," from wer "man, male person" (from PIE root *wi-ro- "man") + wulf (see wolf (n.); also see here for a short discussion of the mythology). Belief in them was widespread in the Middle Ages. Similar formation in Middle Dutch weerwolf, Old High German werwolf, Swedish varulf. In the ancient Persian calendar, the eighth month (October-November) was Varkazana-, literally "(Month of the) Wolf-Men."