aide-de-camp vs equerry

aide-de-camp

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

equerry

noun
  • A personal attendant to a head of state, a member of a royal family, or a national representative. 

  • An officer responsible for the care and supervision of the horses of a person of rank. 

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