borehole vs trepan

borehole

verb
  • To bore a hole of this kind (in). 

noun
  • A hole bored into the ground to collect samples for analysis or to extract oil or water. 

trepan

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. 

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. 

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