How did three sheets to the wind become a marine term?

It refers to having three sails rigged on a sailing boat, a sail was also known as a sheet. I think it was a tactic used in runnng a boat through a storm, erratically, hence becoming a simile for being drunk and unable to walk in a straight line...

The term "sheet" refers to the rope used to secure the sail. It took three ropes to properly secure the sails on the ship. Having three "sheets" loose or "in the wind" would cause the ship to move about much like a drunk person staggering. Hence the original Wording of the phrase "three sheets IN the wind". As far as most can find, the first written instance of this saying was in 1821.