Achillea millefolium vs milfoil

Achillea millefolium

milfoil

noun

  • Any of several similar pungent Eurasian herbs, of the genus Achillea 

  • Common yarrow, Achillea millefolium. 

  • Any plants of the genus Myriophyllum; water milfoil. 

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