catacomb vs cavern

catacomb

noun
  • An underground system of tunnels and chambers with recesses for graves, used (in former times) as a cemetery; a tunnel system used for burying the dead, as in Paris or Ancient Rome. 

cavern

noun
  • An underground chamber. 

  • A large, dark place or space. 

  • A large cave. 

verb
  • To put into a cavern. 

  • To form a cavern or deep depression in. 

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