denigrate vs nitpick over

denigrate

verb
  • To treat as worthless; belittle, degrade or disparage. 

  • To blacken. 

  • To criticise so as to besmirch; traduce, disparage or defame. 

nitpick over

How often have the words denigrate and nitpick over occurred in a corpus of books? (source: Google Ngram Viewer )