funds vs greenback

funds

noun
  • Permanent debts due by a government and paying interest. 

  • Financial resources. 

greenback

noun
  • A unit of American currency issued during the Civil War by the Treasury Department. 

  • The United States dollar. 

  • A wave that has not yet begun to break. 

  • Any bill that is legal tender in the US (originally printed with green and black ink) issued by the Federal Reserve. 

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