three sheets to the wind

Banana Yoshimotoの "Kitchen" を読んでいます。
Yuichi, uncharacteristically, was very drunk. Just as I was thinking that it was off--I didn't see him have that much at dinner--I noticed, with a start, an empty bottle on the floor. Apparently he had been at it while I was cooking; no wonder he was three sheets to the wind. I asked him, amazed, "Youich, did you drink this whole bottle before dinner?"
この "three sheets to the wind" も慣用句ですね。
・Farlex Dictionary of Idioms: slang Extremely drunk, especially to the point of being uncoordinated or out of control. Most likely derived from nautical terminology, in which a "sheet" is the rope that controls the sails of a tall ship; if several sheets are loose or mishandled, the boat's movement becomes unsteady and difficult to control, like that of a drunk person.: On his 21st birthday, Jeff's friends took him to every bar in town until he was three sheets to the wind.

・Collins COBUILD Idioms Dictionary: If someone is three sheets to the wind, they are drunk.: He's probably three sheets to the wind down at Toby's,

・Wiktionary: (idiomatic) Drunk.: That late in the evening, he was three sheets to the wind and had long since stopped making sense.
これは語源が分かりました。