commanding officer vs director

commanding officer

noun
  • The officer in command of, and typically having ultimate authority over, a military unit. 

director

noun
  • One who directs; the person in charge of managing a department or directorate (e.g., director of engineering), project, or production (as in a show or film, e.g., film director). 

  • A device that displays graphical information concerning the targets of a weapons system in real time. 

  • A counselor, confessor, or spiritual guide. 

  • The common axis of symmetry of the molecules of a liquid crystal. 

  • A member of a board of directors. 

  • That which directs or orientates something. 

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