c. 1300, "body or host of knights; knighthood in the feudal social system; bravery in war, warfare as an art," from Old French chevalerie "knighthood, chivalry, nobility, cavalry, art of war," from chevaler "knight," from Medieval Latin caballarius "horseman," from Latin caballus "nag, pack-horse" (see cavalier).
From late 14c. as "the nobility as one of the estates of the realm," also as the word for an ethical code emphasizing honor, valor, generosity and courtly manners. Modern use for "social and moral code of medieval feudalism" probably is an 18c. historical revival.
mid-15c., madamoisell, title applied to an unmarried Frenchwoman, formerly in France the title of any woman not of the nobility, from French mademoiselle (12c.), from a compound of ma dameisele (see damsel), literally "young mistress." Contracted form ma'amselle is attested from 1794, mamsell by 1842.