expiate vs purify

expiate

verb
  • To atone or make reparation for. 

  • To wind up, bring to an end. 

  • To make amends or pay the penalty for. 

  • To purify with sacred rites. 

purify

verb
  • To free from guilt or sin. 

  • To cleanse, or rid of impurities. 

  • To become pure. 

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