lousewort vs selfheal

lousewort

noun
  • Any of very many semiparasitic flowering plants, of the genus Pedicularis, related to wood betony. 

selfheal

noun
  • A small, herbaceous European plant with blue-violet flowers from any species of genus Prunella. 

  • Especially, Prunella vulgaris. 

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