behind the scenes vs nonpublic

behind the scenes

adj
  • Being or working out in secret or out of public view. 

  • Divulging or reporting hidden workings. 

prep
  • behind the scenery and stage area; backstage; among the actors; during the production or rehearsal 

  • In secret; out of public view. 

nonpublic

adj
  • Not open to the public; not available to or shared by the public; private. 

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