boneyard vs potter's field

boneyard

noun
  • A graveyard. 

  • A dumpsite for obsolete or unusable aircraft. 

  • In the game of dominoes, the pile of upside-down pieces that have yet to be used. 

potter's field

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

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