divulge vs prewarn

divulge

verb
  • To indicate publicly; to proclaim. 

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

prewarn

verb
  • To warn beforehand; to forewarn. 

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