brownwort vs selfheal

brownwort

noun
  • A species of figwort or Scrophularia, (Scrophularia vernalis), and other species of the same genus, mostly perennials with inconspicuous coarse flowers. 

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