cloudberry vs thimbleberry

cloudberry

noun
  • The fruit of these plants. 

  • A species of slow-growing bramble, Rubus chamaemorus. 

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. 

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