Jacob's staff vs ocotillo

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. 

ocotillo

noun
  • Any of various succulent plants, not closely related to the cactus, in genus Fouquieria, especially Fouquieria splendens, living in Central America or the southwest United States. 

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