clementine vs grapefruit

clementine

noun
  • A type of small, sweet orange, the result of a cross between a tangerine and Seville orange. 

grapefruit

noun
  • The tree of the species Citrus paradisi, a hybrid of pomelo (Citrus maxima) and sweet orange. 

  • The large spherical tart fruit produced by this tree. 

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