E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A scamp. To shack or shackle is to tie a log to a horse, and send it out to feed on the stubble after harvest. A shack is either a beast so shackled, the right of sending a beast to the stubble, or the stubble itself. Applied to men, a shack is a jade, a stubble-feeder, one bearing the same ratio to a well-to-do man as a jade sent to graze on a common bears to a well-stalled horse. (Anglo-Saxon, sceacul; Arabic, shakal, to tie the feet of a beast.)