adjutant vs pilot officer

adjutant

noun
  • A lower-ranking officer who assists a higher-ranking officer with administrative affairs. 

  • Any bird of the genus Leptoptilos, a branch of the stork family (Ciconiidae) native to India and Southeast Asia. 

  • An assistant. 

adj
  • Assistant; who helps a higher-ranking officer. 

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 adjutant and pilot officer occurred in a corpus of books? (source: Google Ngram Viewer )