bluebell vs lungwort

bluebell

noun
  • Scottish bluebell (harebell) (Campanula rotundifolia) 

  • Spanish bluebell (Hyacinthoides hispanica) 

  • desert bluebell or California bluebell (Phacelia campanularia) 

  • common bluebell (Hyacinthoides non-scripta) 

  • genus Muscari, the grape hyacinth) 

  • Australian royal bluebell (Wahlenbergia gloriosa) 

  • Italian bluebell (Hyacinthoides italica) 

  • Texas bluebell (Eustoma russellianum) 

  • Virginia bluebell (Mertensia virginica) 

lungwort

noun
  • Helleborus niger (family Ranunculaceae, black lungwort) 

  • Any of various European plants, of the genus Pulmonaria (family Boraginaceae), that were once used to treat respiratory disorders. 

  • Mertensia virginica (American lungwort, lungwort oysterleaf, smooth lungwort, tree lungwort) 

  • Mertensia maritima (sea lungwort) 

  • Hieracium murorum (in family Asteraceae, French lungwort or golden lungwort) 

  • Verbascum thapsus (in family Scrophulariaceae, bullock's lungwort, cow's lungwort or clown's lungwort) 

  • Lobaria pulmonaria, syn. Stichta pulmonacea, (in family Lobariaceae, lungwort lichen, lung lichen, tree lungwort) 

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