bonanza vs cash cow

bonanza

noun
  • Anything which is a great source of wealth or yields a large income or return. 

  • The point at which two mother lodes intersect. 

  • A rich mine or vein of silver or gold. 

cash cow

noun
  • Someone or something which is a dependable source of appreciable amounts of money. 

  • A product, service, or enterprise that generates ongoing, high net free cash flows. 

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