harshen vs ossify

harshen

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

  • To render peevish, morose, or austere. 

ossify

verb
  • To become (or cause to become) inflexible and rigid in habits or opinions. 

  • To transform (or cause to transform) from a softer animal substance into bone; particularly the processes of growth in humans and animals. 

  • To grow (or cause to grow) formulaic and permanent. 

  • To calcify. 

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