I think this has been discussed here before, but I can't remember if we found the epexegesis (nor can I liu at the moment). it is given in OED as 'three sheets IN the wind'.

2. three sheets in the wind: very drunk.
a sheet in the wind (or wind's eye) is used occas. = half drunk.
1821 Egan Real Life i. xviii. 385 Old Wax and Bristles is about three sheets in the wind. 1840 R. H. Dana Bef. Mast xx, He+seldom went up to the town without coming down ‘three sheets in the wind’. 1862 Trollope Orley F. lvii, A thought tipsy—a sheet or so in the wind, as folks say. 1883 Stevenson Treas. Isl. xx, Maybe you think we were all a sheet in the wind's eye.

where, it is to be noted, sense 1 goes something like this:
1. A rope (or chain) attached to either of the lower corners of a square sail (or the after lower corner of a fore-and-aft sail), and used to extend the sail or to alter its direction. false sheet: see quot. 1644 in sense 4.


so, it is to be envisioned I think, that three sheets in the wind gives very poor sail control indeed!