Chinese hawthorn vs hawthorn

Chinese hawthorn

noun
  • the fruit of the shrub 

  • Crataegus pinnatifida, a species of shrub that produces a medicinal herb used in Chinese traditional medicine. 

hawthorn

noun
  • Any of various shrubs and small trees of the genus Crataegus having small, apple-like fruits and thorny branches 

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