chrysanthemum vs feverfew

chrysanthemum

noun
  • Any of many flowering perennial plants, of the genus Chrysanthemum, native to China, that have showy radiate heads. 

feverfew

noun
  • A European aromatic perennial herb, Tanacetum parthenium (or Chrysanthemum parthenium or Pyrethrum parthenium), having daisy-like flowers; valued as a traditional medicine, especially for headaches. 

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