Escu'age. n.s. [from escu, French, a shield.]
Escuage, that is service of the shield, is either uncertain or certain. Escuage uncertain is likewise twofold: first, where the tenant by his tenure is bound to follow his lord, going in person to the king's wars against his enemies, either himself, or to send a sufficient man in his place, at his cost, so many days as were agreed upon between the lord and his first tenant at the granting of the fee; and the days of such service seem to have been rated by the quantity of the land so holden: as, if it extend to a whole knight's fee, then the tenant was bound thus to follow his lord forty days. A knight's fee was so much land as, in those days, was accounted a sufficient living for a knight; and that was six hundred and eighty acres as some think, or eight hundred as others, or 15 l. per Annum. Sir Thomas Smith saith that census equestris is 40 l. revenue in free lands. If the law extend but to half a knight's fee, then the tenant is bound to follow his lord, as above is said, but twenty days. The other kind of this escuage uncertain is called castleward, where the tenant by his land is bound, either by himself or by some other, to defend a castle as often as it shall come to his course. Escuage certain is where the tenant is set at a certain sum of money, to be paid in lieu of such uncertain services: as that a man yearly pay for a knight's fee twenty shillings; for half his fee, ten shillings, or some like rate. Cowel.