harebell vs prince's feather

harebell

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

prince's feather

noun
  • Amaranthus hypochondriacus, an ornamental plant. 

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