Jacob's staff vs roseroot

Jacob's staff

noun
  • The ocotillo (Fouquieria splendens), one of certain desert shrubs of southwestern United States and Mexico having slender naked spiny branches that after the rainy season put forth foliage and clusters of red flowers. 

  • Verbascum thapsus, the common mullein. 

  • A single straight rod or staff, pointed and iron-shod at the bottom, for penetrating the ground, and having a socket joint at the top, used, instead of a tripod, for supporting a compass. 

roseroot

noun
  • Rhodiola rosea, a perennial crassulaceous plant with many claimed health benefits that grows in cold regions. 

How often have the words Jacob's staff and roseroot occurred in a corpus of books? (source: Google Ngram Viewer )