boards vs fitness center

boards

noun
  • Structure around a rink for ice hockey. 

  • A hardcover binding on a book. 

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

  • A stage (as in a theater). 

fitness center

noun
  • A gym or fitness club. 

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