ossuary vs undercroft

ossuary

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

undercroft

noun
  • A cellar or vaulted storage room. 

  • A ground-level car park that occupies the base of a building. 

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