Boot Hill vs boneyard

Boot Hill

name
  • Name used for many cemeteries in the American Old West; nickname for any cemetery. 

boneyard

noun
  • A dumpsite for obsolete or unusable aircraft. 

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

  • A graveyard. 

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