aide-de-camp vs pilot officer

aide-de-camp

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

pilot officer

noun
  • The lowest rank of a commissioned officer in the RAF, equivalent to an Army ensign or coronet 

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