banknote vs refund

banknote

noun
  • A piece of paper currency. 

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

refund

noun
  • An amount of money returned. 

verb
  • To return (money) to (someone); to reimburse. 

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