keychain vs watch pocket

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. 

watch pocket

noun
  • A small pocket in the waistband of men's trousers or in other garments for carrying a pocket watch. 

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