porn vs pornographic material

porn

noun
  • Material, usually visual, presenting something desirable in a sensational manner. 

  • A pornographic work. 

  • Material that provides illicit gratification of an obsessive or unhealthy interest in something. 

  • Pornography. 

pornographic material

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