"shallow, flat vessel containing hot water in which another vessel is placed to heat its contents gently," by 1733 (in a cookery book, earlier, 1724 as the name of a meat dish cooked in one), from French bain-marie, from Medieval Latin balneum Mariae, literally "bath of Mary."
According to French sources, perhaps so called for the gentleness of its heating; others credit the name to the supposed inventor, Mary the Jewess, mentioned in early gnostic writings and looked on since 4c. C.E. as a founder of alchemy. Middle English had balne of mary (late 15c.). French bain was used by itself in English in various sense 15c.-17c.; it is from baigner "to bathe" (12c.), from Latin balneare, from balneum "bath" (see balneal).
"child" (of either gender or any age), "son or daughter," Old English bearn "child, son, descendant," from Proto-Germanic *barnan (source also of Old Saxon barn, Old Frisian bern, Old High German barn "child;" lost in modern German and Dutch), from PIE root *bher- (1) "to carry," also "to bear children."
Originally a general English word, in modern English restricted to northern England and Scottish from c. 1700. This was the English form of the original Germanic word for "child" (see child). Dutch, Old High German kind, German Kind are from a prehistoric *gen-to-m "born," from the same root as Latin gignere (see genus and compare kind (n.)). Middle English had bairn-team "brood of children."
The earliest attested use is figurative of the literal one, which is from the popular medieval entertainment of setting dogs on some ferocious beast to bite and worry it. The verb also in Middle English could mean "put a horse or other domestic beast out to feed or graze," and, of persons, "to eat food," also figuratively "feast the eye" (late 14c.). Compare bait (n.). Related: Baited; baiting.