Japanese medlar vs Japanese plum

Japanese medlar

noun

  • The loquat. Eriobotrya japonica, which was formerly thought to be closely related to the medlar 

Japanese plum

noun

  • A fruit tree, Prunus salicina. 

  • A fruit tree, Prunus mume. 

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