Originally: a moth. In later use: a member of the former group Phalaena of moths, originally including all moths other than hawkmoths and later restricted to the geometrids and some pyralids; also (Phalaena), the group itself.
Mid 17th century; earliest use found in John Rowland (fl. c1658). From post-classical Latin phalaena from Hellenistic Greek ϕάλαινα, variant (in late MSS) of ϕάλλαινα a moth, of uncertain origin.