“By the wind“ means sailing into the wind as directly as possible.

“Large“ refers to when the wind is blowing from some compass point behind a ship’s direction of travel, “abaft the beam.”

If a ship ship performed well in both situations, she was said to be a good vessel “by and large“, a phrase we use to this day.

The “by” part of the phrase means “close-hauled.” (This “by” also appears in the term full and by, meaning “sailing with all sails full and close to the wind as possible.”)

When the wind is in that favorable ‘large‘ direction the largest square sails may be set and the ship is able to travel in whatever downwind direction the captain sees fit.

Sorry McD it is “By and large” not “Buy the large”.