keychain vs locket

keychain

noun
  • An ornamental piece holding such a chain or ring. 

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

  • A digital repository for the storage of cryptographic keys. 

locket

noun
  • A pendant that opens to reveal a space used for storing a photograph or other small item. 

  • A small white marking on a cat's coat. 

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