common yarrow vs old man's pepper

common yarrow

noun
  • Achillea millefolium, a flowering plant widespread in the temperate Northern Hemisphere, formerly and sometimes used to stanch the flow of blood. 

old man's pepper

noun
  • Achillea millefolium or common yarrow, a flowering plant native to temperate regions of the Northern Hemisphere. 

How often have the words common yarrow and old man's pepper occurred in a corpus of books? (source: Google Ngram Viewer )