aft vs back end

aft

noun
  • The stern portion of a vessel. 

adj
  • located at the back of a boat, ship, or airplane 

adv
  • At, near, or towards the stern of a vessel (with the frame of reference within the vessel). 

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. 

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