bloodroot vs bloody dock

bloodroot

noun
  • A North American plant, Sanguinaria canadensis, of the poppy family, which has a red root and sap and a single white flower in early spring. 

bloody dock

noun
  • A herb named for its characteristic red or purple veins, used in moderate amounts in salads and as ornamental vegetable, Rumex sanguineus. 

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