harebell vs merrybell

harebell

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

merrybell

noun
  • Synonym of bellwort (“plant of genus Uvularia”) 

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