commanding officer vs overseer

commanding officer

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

overseer

noun
  • An officer responsible for the care of the poor, making out lists of voters and those who had not paid taxes, etc. 

  • The manager of a plantation of slaves. 

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