early 15c., from Late Latin denigrationem (nominative denigratio), noun of action from past participle stem of Latin denigrare (see denigrate).
1520s, from Latin denigratus, past participle of denigrare "to blacken, defame," from de- "completely" (see de-) + nigr-, stem of niger "black" (see Negro). of unknown origin. "Apparently disused in 18th c. and revived in 19th c." [OED]. Related: Denigrated; denigrating.