late 14c., from Old French desdeignier "disdain, scorn, refuse, repudiate," from des- "do the opposite of" (see dis-) + deignier "treat as worthy" (see deign). Related: Disdained; disdaining.
mid-14c., desdegne "scorn, contempt," earlier dedeyne "offended dignity" (c.1300), from Old French desdeigne, from desdeignier (see disdain (v.)). Sometimes in early Modern English shortened to sdain, sdainful. Related: disdainful; disdainfully.