perforate vs trepan

perforate

verb
  • To make a line of holes in (a thin material) to allow separation at the line. 

  • To pierce; to penetrate. 

adj
  • perforated 

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 perforate and trepan occurred in a corpus of books? (source: Google Ngram Viewer )