cash cow vs money-spinner

cash cow

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

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

money-spinner

noun
  • Something that generates a continuous income. 

  • A money spider. 

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