commissioner vs first officer

commissioner

noun
  • An official in charge of a government department, especially a police force. 

  • Someone commissioned to perform certain duties. 

  • A member of a commission. 

  • Someone who commissions something. 

first officer

noun
  • The most senior civil servant in the United States Foreign Service, with responsibility for running an embassy under the authority of and reporting to the ambassador. 

  • Air Transport Auxiliary rank corresponding to Flight Lieutenant in the Royal Air Force. 

  • Women's Royal Naval Service rank corresponding to Lieutenant-Commander in the Royal Navy. 

  • The copilot of an aircraft. 

  • The chief mate of a merchant ship. 

  • The executive officer, second in command of a naval vessel. 

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