depurate vs expiate

depurate

verb
  • To remove impurities from; to purify. 

  • To make impure. 

expiate

verb
  • To purify with sacred rites. 

  • To wind up, bring to an end. 

  • To make amends or pay the penalty for. 

  • To atone or make reparation for. 

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