sully (v.)

early 13c., "to defile or pollute with sin," from Old French soillier "to splatter with mud, to foul or make dirty," originally "to wallow" (12c., Modern French souillier), from souil "tub, wild boar's wallow, pigsty," which is from Latin solium "tub for bathing; seat" (from PIE root *sed- (1) "to sit") or else from Latin suculus "little pig," from sus "pig." The literal meaning "to make dirty on the surface, begrime" is attested from c. 1300 in English. Related: Soiled; soiling.

1580s, from un- (1) "not" + past participle of sully (v.).