harshen vs mollify

harshen

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

  • To render peevish, morose, or austere. 

mollify

verb
  • To soften; to make tender 

  • To ease a burden, particularly worry; make less painful; to comfort. 

  • To appease (anger), pacify, gain the good will of. 

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