blacken (v.)youdaoicibaDictYouDict[blacken 词源字典]
c. 1200, "become black or dark;" early 14c., "make black, darken, dye (hair);" see black + -en (1). Figurative sense of "to besmirch" (with dishonor, etc.) is from early 15c. Related: Blackened; blackening.[blacken etymology, blacken origin, 英语词源]