epicene
Epicene (adj) means describing a group of Greek or Latin nouns that can mean either a male or a female but always keep one fixed grammatical gender.
Etymology
From Late Middle English epicene, epicen, epicin, epcyn, episcen, epycen, epycene, epycyn, ypsen (“(grammar) having only one form for masculine and feminine gender, common”), from Late Latin epicoenos, epicoenus (“of a noun: applicable to either males or females”), Latin epicoenon (“noun applicable to either males or females; grammatical gender of such nouns”), from Ancient Greek ἐπίκοινος (epíkoinos, “common to many people, things, etc.; promiscuous, sluttish”) (compare γένος ἐπίκοινον (génos epíkoinon, “common gender”)), from ἐπι- (epi-, prefix meaning ‘on, upon; on top of; all over’) + κοινός (koinós, “common; general, public”) (ultimately from Proto-Indo-European *ḱóm (“beside, by, near, with”) + *-yós (suffix forming adjectives from noun stems)).