coffee bean vs coffee tree

coffee bean

noun
  • The seed of a tropical plant of the genus Coffea. Prepared by drying, roasting and grinding for making the beverage coffee. 

coffee tree

noun
  • Any tree, such as the Coffea arabica, which yields coffee beans. 

  • Synonym of Kentucky coffeetree 

How often have the words coffee bean and coffee tree occurred in a corpus of books? (source: Google Ngram Viewer )