reliquary vs undercroft

reliquary

noun
  • A container to hold or display religious relics. 

  • A person who owes a balance. 

  • An object that sustains the memory of past people or events. 

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 reliquary and undercroft occurred in a corpus of books? (source: Google Ngram Viewer )