number two vs sub-lieutenant

number two

noun
  • A primary assistant; vice-leader. 

  • A somewhat small town, between a number one and a number three, where the success of a theatrical performance is unlikely to be very great. 

  • The batsman who opens alongside the number one, but does not face the first delivery. 

  • mistress (the other woman in an extramarital relationship, generally including sexual relations) 

  • A pencil with hardness level 2. 

  • A first mate. 

  • Feces; the act of defecation. 

sub-lieutenant

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

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

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