bitter orange vs clementine

bitter orange

noun
  • A citrus tree of the species Citrus ×aurantium, also called Citrus aurantium. 

  • A citrus tree of the species Citrus limetta. 

  • The fruit of these species. 

clementine

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

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