disclosure vs hushing up

disclosure

noun
  • The act of revealing something. 

  • That which is disclosed; a previously hidden fact or series of facts that is made known. 

  • The making known of a previously hidden fact or series of facts to another party; the act of disclosing. 

hushing up

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