bishop's-wort vs red rattle

bishop's-wort

noun
  • fennel flower or devil-in-the-bush (Nigella damascena) 

  • wood betony (Stachys betonica, now Stachys officinalis) 

red rattle

noun
  • Pedicularis palustris (marsh lousewort) 

  • Odontites vernus (red bartsia) 

  • Pedicularis flammea 

  • Any of several plant species of the genus Pedicularis and others. 

How often have the words bishop's-wort and red rattle occurred in a corpus of books? (source: Google Ngram Viewer )