late 15c., "to discolor, to make dirty," of uncertain origin, perhaps from Old French esmorcher "to torture," perhaps also "befoul, stain," from es- "out" (see ex-) + morcher "to bite," from Latin morsus, past participle of mordere "to bite" (see mordant). Sense perhaps influenced by smear. Sense of "dishonor, disgrace, discredit" first attested 1820.
