coffee bean vs mopane

coffee bean

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

mopane

noun
  • A tree, Colophospermum mopane, native to southern Africa. 

  • The mopane worm or mopane moth Gonimbrasia belina 

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