mountain cranberry vs twinberry

mountain cranberry

noun
  • The cowberry, Vaccinium vitis-idaea 

  • The mountain bearberry, Arctostaphylos alpina 

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 mountain cranberry and twinberry occurred in a corpus of books? (source: Google Ngram Viewer )