field marshal vs prefect

field marshal

noun
  • In certain nations the highest military rank, ranking below only the commander in chief; now essentially disused. 

prefect

noun
  • A commander. 

  • The head of a department in France. 

  • A school pupil in a position of power over other pupils. 

  • An official of Ancient Rome who controlled or superintended a particular command, charge, department, etc. 

  • The head of a county in Albania or Romania. 

  • The head of a prefecture in Japan. 

How often have the words field marshal and prefect occurred in a corpus of books? (source: Google Ngram Viewer )