foxhole vs trephine

foxhole

verb
  • To dig a military foxhole into, or convert into a foxhole by digging. 

  • To drive into a military foxhole. 

noun
  • The burrow in the ground where a fox lives. 

  • A small pit dug into the ground as a shelter for protection against enemy fire. 

trephine

verb
  • To perforate with a trephine. 

  • To use a trephine during surgery. 

noun
  • A surgical instrument with a cylindrical blade used to remove a circular section of tissue, f.e. bone or cornea; a trepan. 

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