abaft vs astern

abaft

adv
  • On the aft side; in the stern. 

prep
  • Behind; toward the stern relative to some other object or position; aft of. 

astern

adv
  • In the direction of the stern; backward (motion); to the rear. 

  • Behind (a vessel); in the rear. 

adj
  • Behind a vessel; having a bearing of 180 degrees from ahead. 

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