callus vs develop

callus

verb
  • To form such hardened tissue. 

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

  • 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. 

  • 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. 

develop

verb
  • To place one's pieces actively. 

  • To progress through a sequence of stages. 

  • To bring out images latent in photographic film. 

  • To advance; to further; to promote the growth of. 

  • To acquire something usually over a period of time. 

  • To change with a specific direction, progress. 

  • To create. 

  • To cause a ball to become more open and available to be played on later. Usually by moving it away from the cushion, or by opening a pack. 

  • To change the form of (an algebraic expression, etc.) by executing certain indicated operations without changing the value. 

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