midshipman vs sergeant major

midshipman

noun
  • A midshipman fish. 

  • An officer of the lowest rank in several navies; especially, a trainee officer. 

sergeant major

noun
  • A fish, the pintano (Abudefduf saxatilis). 

  • An appointment (not a rank) in the British Army and Royal Marines, denoting the most senior non-commissioned officer in a battalion, regiment or company. 

  • A senior non-commissioned appointment in the Army of a company or unit, directly responsible to the officer in charge for their soldiers' performance, standards, discipline, morale, welfare, et al, that can be held by a Warrant Officer or above. 

  • The most senior rank of non-commissioned officer in the United States Army, ranking above a first sergeant. In the United States Marine Corps it ranks above First Sergeant and is equal in grade to Master Gunnery Sergeant. 

  • An appointment (not a rank) in the Singapore Army and National Cadet Corps, denoting the most senior non-commissioned officer in a battalion, regiment, company or unit. 

How often have the words midshipman and sergeant major occurred in a corpus of books? (source: Google Ngram Viewer )