petty cash vs small change

petty cash

noun
  • Cash available for trivial purchases, especially limited funds for employees to use without close supervision. 

small change

noun
  • A minor or insignificant amount of money. 

  • Coins of little value kept in one's pocket or bag. 

  • A person or thing of little importance or value. 

How often have the words petty cash and small change occurred in a corpus of books? (source: Google Ngram Viewer )