postern vs rearward

postern

adj
  • Situated at the rear; posterior. 

noun
  • A back gate, back door, side entrance, or other gateway distinct from the main entrance. 

  • A subterranean passage communicating between the parade and the main ditch, or between the ditches and the interior of the outworks. 

rearward

adj
  • Toward the back or rear of something. 

noun
  • The last troop; the rear of an army; a rear guard. 

  • The part that comes last or is situated in the rear; conclusion, wind-up. 

adv
  • Toward the back or rear of something. 

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