episcopus

Episcopus, episcopi, m., is second declension and a straight import from Greek episkopos, "overseer" - epi plus skopeo, one who watches over. Classical Latin uses it rarely and secularly, for an inspector or a market officer, and that plain sense is still audible in the earliest Christian texts: the episcopus of the New Testament is not yet the medieval prince-bishop.

By the charter period it is one of the commonest nouns in the corpus, usually abbreviated eps or epc with a stroke through it. His seat is the sedes, his territory the dioecesis, and the adjective is episcopalis. English "bishop" is the same word ground down through Old English biscop, which is why "bishopric" and "episcopal" look unrelated but are not.