Mid 19th century (in an earlier sense). From post-classical Latin psilosis action of stripping flesh and its etymon ancient Greek ψίλωσις action of stripping hair or flesh, in medieval Greek also action of writing or pronouncing with a smooth breathing or unaspirated consonant from ψιλοῦν to strip bare, make bald, in Hellenistic Greek also to write or pronounce with a smooth breathing or unaspirated consonant (from ψιλός bare, bald: see psilo-) + -ωσις.