callus vs efface

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. 

efface

verb
  • Of the cervix during pregnancy, to thin and stretch in preparation for labor. 

  • To make oneself inobtrusive as if due to modesty or diffidence. 

  • To cause to disappear as if by rubbing out or striking out. 

  • To erase (as anything impressed or inscribed upon a surface); to render illegible or indiscernible. 

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