cover-up vs imposture

cover-up

noun
  • An attempt to conceal or disguise something, especially a wrongdoing or a mistake. 

  • An item of clothing to be worn over a swimsuit while not in the water. 

imposture

noun
  • The act or conduct of an impostor; deception practiced under a false or assumed character; fraud or imposition 

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