|Definition - A term from Latin and Greek grammar that is used to label nouns that can denote either sex without changing their grammatical gender.|
Etymology - The term derives from the Latin epicoenus, common (ultimately from from the Greek epi-, on + koinos, common.)
Oxford English Dictionary - Its first citation is from circa 1528:
"Wherefor all gendyrs dysconte[nt] be … The dubyum & the epysyn Also."
(Impeachm. Wolsey in Furniv. Ballads fr. MSS. I. 356)