betony vs selfheal

betony

noun
  • Any plant of the genus Pedicularis (louseworts). 

  • Stachys officinalis (syn. Betonica officinalis, an herb used in traditional European medicine. 

  • Any plant of the genus Stachys. 

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 betony and selfheal occurred in a corpus of books? (source: Google Ngram Viewer )