Definition of "nosebag"

During peace in all marches of five hours it is advisable to feed once en route, if possible immediately after the horses have had a good drink. The bit being removed, the nosebag is to be buckled well up, to allow the horse to reach the feed easily and prevent him tossing his head and spilling the grain. Half-way through the feed it may require readjusting for the same reason. Horses that toss their heads persistently should have the top of the bag tightened round the face by a rubber, cord, or strap, to prevent waste. When the horse ceases to feed he should be allowed to graze and the nosebag is to be turned inside out to dry.

1908 Animal Management. Prepared in The Veterinary Department for General Staff, War Office, London: Published by His Majesty's Stationery Office

For this man Filmer, you must understand, was not one of those men who are lightly kept from the tea-table. A hearty trencherman, and particularly fond of his five o’clock couple of cups and bite of muffin, he had until this afternoon always been well up among the leaders in the race for the food-trough. If one thing was certain, it was that only the machinations of some enemy could be keeping him from being in the drawing-room now, complete with nosebag.

1925 P. G. Wodehouse. "Carry On, Jeeves" pub. Herbert Jenkins