Q From Benjamin Weatherston: How does the term three sheets to the wind denote drunkenness?
A It’s a sailor’s expression, from the days of sailing ships. The terminology of sailing ships is excessively complicated and every time I refer to it people write in to say I’ve got it wrong, usually contradicting each other. So treat what follows as a broad-brush treatment, open to dispute on fine points.
We ignorant landlubbers might think that a sheet is a sail, but it’s actually a rope (always called a line in sailing terminology), or sometimes on really big ships a chain, which is attached to the bottom corner of a sail. The word actually comes from an Old English term for the corner of a sail. The sheets were as vital in the days of three-masted square-rigged sea-going ships as they are today, since they trim the sail to the wind. If they run loose, the sail flutters about in the wind and the ship wallows off its course out of control.
Extend this idea to sailors on shore leave, staggering back to the ship after a good night on the town, well tanked up. The irregular and uncertain locomotion of these jolly tars must have reminded onlookers of the way a ship moved in which the sheets were loose. Perhaps one loose sheet might not have been enough to get the image across, so the speakers borrowed the idea of a three-masted sailing ship with three sheets loose, so the saying became three sheets in the wind.
Our first written example comes from that recorder of low life, Pierce Egan, in his Real life in London of 1821. But it must surely be much older.
The version you give, incidentally, is comparatively recent, since the older one (the only one given in the big Oxford English Dictionary) is three sheets in the wind. However, online searches show that your version is now much more as common than the one containing in, so it may be that some day soon it will be the only one around. The version with to seems to be gaining ground because so many people think that a sheet is a sail.