paramour (n.)

early 14c., "a lover or wooer" of either sex, noun use of adverbial phrase par amour (c. 1300) "passionately, with strong love or desire," from Anglo-French and Old French par amour, from accusative of amor "love," from amare "to love" (see Amy). Originally a term for Christ (by women) or the Virgin Mary (by men), it came to mean "darling, sweetheart" (mid-14c.) and "wife, husband," also, in a bad sense, "mistress, concubine; (a woman's) male lover; clandestine lover" (late 14c.) which from 17c. became the only sense, except in poetry.