fob vs keychain

fob

noun
  • A small ornament attached to such a chain. 

  • A little pocket near the waistline of a pair of trousers or in a waistcoat or vest to hold money or valuables, especially a pocketwatch. 

  • A short chain or ribbon to connect such a pocket to the watch. 

  • A hand-held remote control device used to lock/unlock motor cars etc. 

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. 

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