dehumanize vs harshen

dehumanize

verb
  • To take away humanity; to remove or deny human qualities, characteristics, or attributes; to impersonalize. 

harshen

verb
  • To make, or to become harsh; render hard and rough. 

  • To render peevish, morose, or austere. 

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