A more thorough explanation:

Definition: Affidatus (af-uh-dey-tuhs), n. [Law Latin] Historical term for a tenant who owes fealty to a lord.

Example: In medieval England, a knight who held land from a lord was an affidatus. The knight swore an oath of loyalty to the lord and promised to defend the land against enemies.

Explanation: The term affidatus refers to a type of feudal relationship between a lord and a tenant. The tenant, or affidatus, owed fealty to the lord, which meant they had to be loyal and obedient. In exchange, the lord granted the tenant land to use and protect. The example illustrates how a knight who held land from a lord was an affidatus and had certain obligations to fulfill.