necklace vs pearl necklace

necklace

noun
  • Anything resembling a necklace in shape. 

  • A device used in necklacing (an informal execution); a rubber tyre that is filled with petrol. It is placed around the victim's chest and arms, and set on fire. 

  • An article of jewelry that is worn around the neck, most often made of a string of precious metal, pearls, gems, beads or shells, and sometimes having a pendant attached. 

verb
  • To informally execute by necklacing; by setting on fire a petrol-filled rubber tyre which has been put around the bound victim's neck. 

pearl necklace

noun
  • Used other than figuratively or idiomatically: see pearl, necklace. 

  • A sexual act whereby semen is ejaculated onto a partner's upper chest, breasts and/or throat. 

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