boards vs celluloid

boards

noun
  • A stage (as in a theater). 

  • A hardcover binding on a book. 

  • Examinations given for entry to college or to qualify for a profession. 

  • Structure around a rink for ice hockey. 

celluloid

noun
  • The genre of cinema; film. 

  • Any of a variety of thermoplastics created from nitrocellulose and camphor, once used as photographic film. 

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