first officer vs legate

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. 

legate

noun
  • An ambassador or messenger. 

  • The deputy of a provincial governor or general in ancient Rome. 

  • A deputy representing the pope, specifically a papal ambassador sent on special ecclesiastical missions. 

verb
  • To leave as a legacy. 

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