old man's pepper vs thousand-leaf

old man's pepper

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

thousand-leaf

noun
  • Achillea millefolium or common yarrow, a flowering plant widespread in the temperate Northern Hemisphere, featuring finely divided leaves. 

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