1815-25; < French,Middle French, translation of Medieval Latinbalneum Mariae literally, bath of Mary, reputed to be a Jewish alchemist who devised such a heating technique, and sometimes identified with Moses' sister Miriam
a vessel for holding hot water, in which sauces and other dishes are gently cooked or kept warm
C19: from French, from Medieval Latin balneum Mariae, literally: bath of Mary, inaccurate translation of Medieval Greek kaminos Marios, literally: furnace of Miriam, alleged author of a treatise on alchemy
1822, 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. Middle English had balne of mary (late 15c.).