Old nautical terms have modern usage

"Another interesting paired term is 'by and large.' The idiom seems to have lost most of its meaning today, except as a mild qualifier for a judgment. The phrase survives in such constructions as 'by and large, I think she's the best candidate.' The phrase is synonymous with 'overall' or 'considering all the facts.'

In square-rigged sailing ships, to sail 'large' is to sail with the wind at the stern, to go the way the wind blows. When sailing large, a ship would put on as much sail as was safe under the circumstances and would typically try to maximize her speed. She could be sighted more easily by lookouts, friend and foe alike, because of the large mass of canvas she deployed.

In sailing 'by,' on the other hand, a ship was trying to go into the wind. The sails would be rigged fore and aft, that is, lengthwise. Some ships were better built to sail into the wind, and in naval combat in particular, it was a decisive tactical advantage. But all ships had to sail into the wind from time to time.

The expression 'by and large,' then, means 'under all circumstances.' Ship crews would eventually go everywhere, by and large"