If you stop and think about a common, everyday expression, sometimes what you think is that it makes no sense. For example, “by and large” means “generally” or “for the most part.” The phrase has been around at least since the early 1700s (“Tho’ he trys every way, both by and large, to keep up with his Leader.”), and it’s still common (“The virtue of sound broadcasting was that, by and large, the content mattered more than anything else.”)
But why would “by” be matched with “large”, and why, when those two words are combined, would the phrase take on that meaning? The answer lies out at sea. No, really; it was originally a nautical expression. It has to do with sailing ships. When a sailing ship was traveling with the wind — that is, when the wind was blowing from any direction that was behind the ship, even by a little bit — the nautical term for that was “sailing large.”
“Large” in this case doesn’t have anything to do with the size of the sails; it’s the sense of the word you can also see in the phrase “at large” — it means freedom. When the wind is blowing from behind a sailing ship, it’s an easy matter to set a course in that direction.
The ocean wind doesn’t always blow in the direction you want to go, of course. But sailing ships had ways of managing that situation. It depended on the ship, but by adjusting the sails carefully it was possible to make progress in the general direction the wind was blowing from, as long as you didn’t steer so that the wind was blowing from directly in front of the ship. When you were doing that, the nautical term was “sailing by the wind”. Once again, “by” doesn’t mean what you might think at first; in that context “by” means “toward.”
It’s widely agreed that wind doesn’t blow from both behind and in front of a ship at the same time, and it was just as well accepted that a sailing ship could “sail large” or “sail by the wind,” but not both at once. But the crew had to be ready to cope with either situation. The phrase “by and large” initially had to do with being prepared for all possible sailing conditions, and later got adopted ashore to mean all possible conditions, sail-related or not. And by and large, the phrase has been used ever since, even though its original nautical sense blew away a long time ago.
