crown jewels vs family jewels

crown jewels

noun
  • The jewelry that accompany the office of rulership in a monarchy, i.e. crown, scepter, signet ring, etc. 

  • The male genitalia. 

family jewels

noun
  • Used other than figuratively or idiomatically: see family, jewels. 

  • Testicles. 

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