A person who serves a lord is typically referred to as a vassal or a servant. They provide assistance to the lord in various capacities, such as managing land, providing military service, or attending to the lord's needs.
a vassal or a serf google them
A vassal
the vikings
A vassal
Serfs
it is a vassal
The lord fought in battle when needed, managed his estates and served his lord. The lady managed the household, bore and raised children.
Typically most Englishmen served fourty-five days for their lord.
Charles Townshend
I have faithfully served the Lord with all my heart.
They were the serfs.
They both served a lord and worked on the manor.