foxberry vs twinberry

foxberry

noun
  • The berry of this plant. 

  • The plant cowberry or lingonberry, Vaccinium vitis-idaea. 

twinberry

noun
  • Its fruit, a bitter edible black berry containing several small seeds. 

  • A North American species of honeysuckle, Lonicera involucrata. 

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