commissioner vs sub-lieutenant

commissioner

noun
  • An official in charge of a government department, especially a police force. 

  • Someone commissioned to perform certain duties. 

  • A member of a commission. 

  • Someone who commissions something. 

sub-lieutenant

noun
  • A commissioned officer of the Royal Navy ranking above a midshipman and below a lieutenant. 

  • A commissioned officer of the navy ranking above an acting sub-lieutenant and below a lieutenant. 

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