free lunch vs small change

free lunch

noun
  • Something obtained without any payment, obligation or effort. 

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 free lunch and small change occurred in a corpus of books? (source: Google Ngram Viewer )