Aids

In feudal law, originally mere benevolences granted by a tenant to his lord, in times of distress; but at length the lords claimed them as of right. They were principally three:
(1) To ransom the lord's person, if token prisoner;
(2) to make the lord's eldest son and heir apparent a knight;
(3) to give a suitable portion to the lord's eldest daughter on her marriage. Abolished by 12 Car. II. c. 24. Also, extraordinary grants to the crown by the house of commons, and which were the origin of the modern system of taxation. 2 Bl. Comm. 63, 64.

— Reasonable aid. A duty claimed by the lord of the fee of his tenants, holding by knight service, to marry his daughter, etc. Cowell.