ossuary vs urnfield

ossuary

noun
  • A container, receptacle, or building, such as an urn or vault, for holding the bones of the dead. 

urnfield

noun
  • Ground used as a cemetery in Bronze Age Europe, in which the ashs of cremations were buried in cinerary urns. 

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