back end vs rearward

back end

noun
  • The rear, back, or unseen portion (of something). 

  • The processing of spent fuel from a nuclear reactor into reusable materials. 

  • That part of a hardware or software system that is farthest from the user; the internals rather than the user interface. 

  • The latter end of any given time, especially the latter part of the year; autumn; late autumn. 

  • Money paid on a contingent deferred basis, for example, as a proportion of the profits or revenue of a work. 

rearward

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

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

adj
  • Toward the back or rear of something. 

adv
  • Toward the back or rear of something. 

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