Aaron's rod vs Jacob's staff

Aaron's rod

noun
  • Verbascum thapsus, the great mullein, common mullein, or hag-taper. 

  • Hylotelephium telephium (syn. Sedum telephium; orpine, livelong, or live-forever). 

  • A rod-shaped molding decorated with an entwined snake, and sometimes leaves, vines, and/or scrolls. 

  • Goldenrod, the Solidago genus of North American plants with yellow flowers. 

Jacob's staff

noun
  • 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. 

  • 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. 

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