free pass vs get-out-of-jail-free card

free pass

noun
  • An exemption from normal processes. 

  • An intentional walk. 

  • A document entitling the bearer to free transportation. 

get-out-of-jail-free card

How often have the words free pass and get-out-of-jail-free card occurred in a corpus of books? (source: Google Ngram Viewer )