handcuffs vs keychain

handcuffs

noun
  • A fastening consisting of two metal rings, designed to go around a person's wrists, and connected by a chain or hinge. 

keychain

noun
  • A chain or ring to which a key may be attached. 

  • An ornamental piece holding such a chain or ring. 

  • A digital repository for the storage of cryptographic keys. 

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