subs. phr. (racing).The last two months of the racing season, commencing with October: also as adj. [Properly (Scots) = the latter part of autumn.] Hence BACK-ENDER = a horse entered for a race late in the season.
1820. Blackwoods Magazine, Oct., 3. When you did me the honour to stop a day or two at last BACK-END.
1883. HAWLEY SMART, Hard Lines, xxix. Most of what I got over that steeplechase I dropped at the BACK-END over the October handicaps.
1883. Daily Telegraph, 30 April, 3. 6. And neither [horse] could beat Palermo on BACK-END form.
c. 1889. The Sporting Times [A Dictionary of Slang, Jargon & Cant]. Lord Bradfords horse evidently likes the Doncaster course, and he is undoubtedly a BACK-ENDER.