crown jewels vs headband

crown jewels

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

  • The male genitalia. 

headband

noun
  • A strip of fabric attached to the top of the spine of a book; used as decoration and reinforcement. 

  • A strip of fabric worn around the head. 

  • A hair-accessory, made of a flexible material and curved like a horseshoe, for holding one's hair back. 

  • A thin slip of iron on the tympan of a printing-press. 

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