cup of tea vs herbal tea

cup of tea

noun
  • Used other than figuratively or idiomatically: see cup, tea. A cup or mug with tea in it. 

  • three 

  • Whatever suits or interests one. 

herbal tea

noun
  • A beverage made by infusing the leaves of various herbs, generally not including true tea (Camellia sinensis). 

How often have the words cup of tea and herbal tea occurred in a corpus of books? (source: Google Ngram Viewer )