cash cow vs moneymaker

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. 

moneymaker

noun
  • Someone or something that earns or makes money; anything lucrative or profitable. 

  • (usually a woman's) butt, ass, rear end 

  • A lady’s breast. 

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