DO vs trephine

DO

noun
  • a Doctor of Osteopathic Medicine 

  • a direct object 

  • dissolved oxygen 

trephine

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

verb
  • To use a trephine during surgery. 

  • To perforate with a trephine. 

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