"belonging to or including both sexes," mid-15c., epycen, originally a grammatical term for nouns that may denote either gender, from Latin epicoenus "common," from Greek epikoinos "common to many, promiscuous," from epi "on" (see epi-) + koinos "common" (see coeno-). English has no need of it in its grammatical sense. Extended sense of "characteristic of both sexes" first recorded in English c.1600; that of "effeminate" is from 1630s.