coadjutor vs sub-lieutenant

coadjutor

noun

  • An assistant to a bishop. 

  • An assistant or helper. 

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 coadjutor and sub-lieutenant occurred in a corpus of books? (source: Google Ngram Viewer )