bilberry vs fraughan

bilberry

noun
  • Vaccinium myrtillus, the wild European blueberry of the cowberry family. 

  • The shrub of the above-mentioned plant. 

fraughan

noun
  • The bilberry or whortleberry (Vaccinium myrtillus). 

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