excavate vs trepan

excavate

verb
  • To make a hole in (something); to hollow. 

  • To uncover (something) by digging. 

  • To remove part of (something) by scooping or digging it out. 

noun
  • Any member of a major grouping of unicellular eukaryotes, of the clade Excavata. 

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