aide-de-camp vs flying officer

aide-de-camp

noun
  • A military officer who serves as an adjutant to a higher-ranking officer, prince or other high political dignitary. 

flying officer

noun
  • A person holding a rank in the RAF, between that of pilot officer and flight lieutenant, equivalent to an Army lieutenant or Royal Navy sublieutenant. 

How often have the words aide-de-camp and flying officer occurred in a corpus of books? (source: Google Ngram Viewer )