callus vs grit

callus

noun
  • The material of repair in fractures of bone; a substance exuded at the site of fracture, which is at first soft or cartilaginous in consistency, but is ultimately converted into true bone and unites the fragments into a single piece. 

  • A shining area on the frons of many species of Tabanomorpha (horse flies and relatives). 

  • The new formation over the end of a cutting, before it puts out rootlets. 

  • A hardened area of the skin (especially on the foot or hand) caused by repeated friction, wear or use. 

verb
  • To form such hardened tissue. 

grit

noun
  • A collection of hard small materials, such as dirt, ground stone, debris from sandblasting or other such grinding, or swarf from metalworking. 

  • A hard, coarse-grained siliceous sandstone; gritstone. Also, a finer sharp-grained sandstone, e.g., grindstone grit. 

  • Strength of mind; great courage or fearlessness; fortitude. 

  • Coarsely ground corn or hominy used as porridge. 

  • Inedible particles in food. 

  • Husked but unground oats. 

  • A measure of the relative coarseness of an abrasive material such as sandpaper, the smaller the number the coarser the abrasive. 

  • Sand or a sand–salt mixture spread on wet and, especially, icy roads and footpaths to improve traction. 

verb
  • To cover with grit. 

  • Apparently only in grit one's teeth: to clench, particularly in reaction to pain or anger. 

How often have the words callus and grit occurred in a corpus of books? (source: Google Ngram Viewer )