first officer vs warden

first officer

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

  • 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 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. 

warden

noun
  • A chief administrative officer of a prison. 

  • An official charged with supervisory duties or with the enforcement of specific laws or regulations; such as a game warden or air-raid warden 

  • A variety of pear. 

  • A governing official in various institutions 

verb
  • To carry out the duties of a warden. 

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