A more thorough explanation:

FEODI FIRMARIUS

Feodi firmarius refers to a tenant who holds a fee farm.

In history, a fee farm was a type of land tenure where the tenant paid a fixed annual rent to the landlord in exchange for the right to use and profit from the land. The tenant who held this type of land was called a feodi firmarius.

An example of a feodi firmarius would be a farmer who rented a piece of land from a lord in medieval times. The farmer would pay a fixed annual rent to the lord and in return, would be allowed to use the land to grow crops or raise livestock.