divulge vs let cat out of the bag

divulge

verb
  • To make public or known; to communicate to the public; to tell (information, especially a secret) so that it may become generally known. 

  • To indicate publicly; to proclaim. 

let cat out of the bag

How often have the words divulge and let cat out of the bag occurred in a corpus of books? (source: Google Ngram Viewer )