auger vs trepan

auger

noun
  • A tool used to bore holes in the ground, e.g. for fence posts 

  • A snake or plumber's snake (plumbing tool). 

  • A hollow drill used to take core samples of soil, ice, etc. for scientific study. 

  • A carpenter's tool for boring holes longer than those bored by a gimlet. 

verb
  • To use an auger; to drill a hole using an auger. 

  • To proceed in the manner of an auger. 

trepan

noun
  • A tool used to bore through rock when sinking shafts. 

  • A surgical instrument used to remove a circular section of bone from the skull; a trephine. 

verb
  • To create a large hole by making a narrow groove outlining the shape of the hole and then removing the plug of material remaining by less expensive means. 

  • To use a trepan; to trephine. 

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