cowberry vs partridgeberry

cowberry

noun
  • The berry of this shrub. 

  • A shrub native to the cool temperate areas of the Northern Hemisphere (Vaccinium vitis-idaea). 

partridgeberry

noun
  • The berry of such a plant. 

  • lingonberry, Vaccinium vitis-idaea 

  • teaberry, Gaultheria procumbens 

  • squaw vine, Mitchella repens 

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