crypt vs potter's field

crypt

noun
  • An underground vault, especially one beneath a church that is used as a burial place. 

  • Any of the genus Cryptopus of orchids of Madagascar and Mauritius. 

  • A small pit or cavity in the surface of an organ or other structure. 

  • Any of the genus Cryptocoryne of aquatic plants of southern and southeastern Asia. 

potter's field

noun
  • A public place where strangers, paupers, and criminals are buried. 

How often have the words crypt and potter's field occurred in a corpus of books? (source: Google Ngram Viewer )