Trousers expanding right down to or simply just underneath the leg.
breeches visiting the knee, and buckled or fastened there; smallclothes.
See under Breeches.
pants closing over the leg
Breeches that get to to the knee or just below it; specifically, a close-fitting garment covering the leg and the reduced the main body, worn generally speaking right from the start regarding the eighteenth century until about 1815. See knickerbocker, 3.