inseminate vs trephine

inseminate

verb
  • To impregnate (to cause to become pregnant). 

  • To sow (to disperse or plant seeds). 

  • To fill with one's semen. 

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 inseminate and trephine occurred in a corpus of books? (source: Google Ngram Viewer )