blacken

[blak-uh n] /ˈblæk ən/
verb (used with object)
1.
to make black; darken.
2.
to speak evil of; defame:
to blacken a person's reputation.
verb (used without object)
3.
to grow or become black.
Origin
1250-1300; Middle English; see black, -en1
Related forms
blackener, noun
Synonyms
2. denigrate, smear, slander, villify, libel, traduce, calumniate.
British Dictionary definitions for blacken

blacken

/ˈblækən/
verb
1.
to make or become black or dirty
2.
(transitive) to defame; slander (esp in the phrase blacken someone's name)
Word Origin and History for blacken
v.

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.