bellflower vs harebell

bellflower

noun
  • Any flowering plants in the genus Campanula. 

  • A flower of one of these plants, which is shaped like a bell. 

  • Flowering plants in the genera, Campanulastrum, Codonopsis, or Platycodon, in the family Campanulaceae. 

  • Any flowering plant in genus Uvularia. 

harebell

noun
  • A perennial flowering plant, Campanula rotundifolia, native to the Northern Hemisphere, with blue, bell-like flowers. 

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