c.1400, "to bathe in a steam bath," from Old French estuver (French étuver) "bathe, stew," of uncertain origin. Common Romanic (cf. Spanish estufar, Italian stufare), possibly from Vulgar Latin *extufare "evaporate," from ex- "out" + *tufus "vapor, steam," from Greek typhos "smoke." Cf. Old English stuf-bæþ "hot-air bath;" see stove. Meaning "to boil slowly, to cook meat by simmering it in liquid" is attested from early 15c. The meaning "to be left to the consequences of one's actions" is from 1650s, from figurative expression to stew in one's own juices. Slang stewed "drunk" first attested 1737.
c.1300, "vessel for cooking," from stew (v.). Later "heated room" (late 14c.). The noun meaning "stewed meat with vegetables" is first recorded 1756; Irish stew is attested from 1814. The obsolete slang meaning "brothel" (mid-14c., usually plural, stews) is from an earlier sense of "public bath house," carried over from Old French and reflecting the reputation of such houses.