keychain vs keyring

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. 

keyring

noun
  • A ring, normally of metal or plastic, for holding keys together. 

  • A set of data holding linked encryption keys. 

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