first lieutenant vs underling

first lieutenant

noun
  • The second lowest rank of a commissioned officer in the United States Army, Air Force, or Marine Corps, ranking above a second lieutenant and below a captain. The rank of first lieutenant is equivalent to the naval rank of lieutenant junior grade. 

  • An equivalent rank in other military forces. 

underling

noun
  • A subordinate, or person of lesser rank or authority. 

  • A low, wretched person. 

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