fat cat vs millionaire

fat cat

noun
  • A rich person who contributes to a political campaign. 

  • Any affluent person who is perceived to have profited from the labour of others. 

  • Used other than figuratively or idiomatically: see fat, cat. 

millionaire

noun
  • A person whose net worth is at or greater than one million units of the local currency; a multimillionaire. 

  • A person whose net worth is at or greater than one million units of the local currency, but less than two million. 

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