aback adv [ a prep + back]
1 in prep phr aback of: Behind. [OED3 aback adv. P5 1743→; “in later use chiefly Sc., Eng. regional, U.S. regional, and Caribbean”]
1755 in 1892 Plymouth MA Records 2.168, Taken up and Impounded . . Two Small Boores one of Which has a small Black spott a Little aback of his sholder. 1783 in 1916 Mereness Travels 663 KY, Fern Creek is lost in ponds and low flat land a back of the Falls. 1836 Edward Hist. TX 79, Those districts . . aback of the older settled ones. 1938 Matschat Suwannee R. 162 nFL, sGA, He heerd somethin’ gruntin’ a-back of some gallberry bushes. 1943 LANE Map 723 seMA, 1 inf, A-back of [for “behind”]. 1996–97 in 2004 Montgomery–Hall Dict. Smoky Mt. Engl. 3 wNC, eTN, A-back of [=behind].
2 Ago. [OED3 aback adv. 4 1768→; “Chiefly regional (orig. Sc.)”]
1831 Amer. Mercury (Hartford CT) 11 Apr /1, As our neighbours of the Times are fond of contrasting results with ‘years aback,’ we hope they will not fail to compare this with the result of 1829. 1847 Dollar Newspaper (Philadelphia PA) 21 July /2, Those who recollect him years aback in connection with the New York American, will, of course, make the Franklin House, Philadelphia, their stopping place. 1895 Black Cat Dec 20 CA, Adolphe and me set up backin’ and minin’ together five years aback. 1929 Alton Eve. Telegraph (IL) 20 July 4/1, The old time “mellerdrammer” which used to glorify for us the heroes and heroines of the “ten-twent-thirt” cent shows of 40 years aback, are coming back into their own with vigor. 1950 Dunkirk Eve. Observer (NY) 10 Mar 15/3, [Letter:] A few years aback Eddie took a gallant bunch to Chicago to play in the National Catholic League. 1967 DARE (Qu. A17, If it was 1960 and you were speaking of something that happened in 1950, you might say “That was ten _____.”) Inf TN11, Years aback. 1982 Progress (Clearfield PA) 30 Aug 4/2, Mr. Lutz . . did a great job as Scoutmaster of a Boy Scout troop down at Winburne some years aback. 1993 Daily Independent (Kannapolis NC) 14 Jan 1/3, He’s even resumed playing golf, something he gave up some years aback.