boneyard vs cem

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. 

cem

noun
  • cemetery 

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