commanding officer vs servant

commanding officer

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

servant

noun
  • A person of low condition or spirit. 

  • One who serves another, providing help in some manner. 

  • A person who dedicates themselves to God. 

  • One who is hired to perform regular household or other duties, and receives compensation. As opposed to a slave. 

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