greenback vs one-spot

greenback

noun
  • The United States dollar. 

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

  • 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. 

one-spot

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