cavern vs cellar door

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. 

cellar door

noun
  • A door leading to a cellar. 

  • In phonaesthetics, a quintessential example of an inherently pleasant-sounding phrase irrespective of its meaning. 

  • Part of a winery from which wine may be sampled or purchased. 

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