thimbleberry vs whitebark raspberry

thimbleberry

noun
  • The fruit of the above plant. 

  • Rubus parviflorus, a species of Rubus, native to western and northern North America, from Alaska east to Ontario and Minnesota, and south to northern Mexico. 

  • The black raspberry, Rubus occidentalis. 

whitebark raspberry

noun
  • The dark purple composite fruit of this plant, similar to a raspberry. 

  • A deciduous, viny shrub (Rubus leucodermis) with a pale, whitish bark. 

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