late 14c., from Old French harpie (14c.), from Greek Harpyia (plural), literally "snatchers," probably related to harpazein "to snatch" (see rapid). Metaphoric extension to "greedy person" is c.1400.
In Homer they are merely personified storm winds, who were believed to have carried off any person that had suddenly disappeared. In Hesiod they are fair-haired and winged maidens who surpass the winds in swiftness, and are called Aello and Ocypete; but in later writers they are represented as disgusting monsters, with heads like maidens, faces pale with hunger, and claws like those of birds. The harpies ministered to the gods as the executors of vengeance. ["American Cyclopædia," 1874]