banknote vs bullion

banknote

noun
  • A piece of paper currency. 

  • A promissory note issued by a bank, payable at a given time to a specific beneficiary. 

bullion

noun
  • A bulk quantity of precious metal, usually gold or silver, assessed by weight and typically cast as ingots. 

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