What does "amercement" mean?

Amercement: The infliction of a penalty at the discretion of the court; also, a mulct or penalty thus imposed. It differs from a fine,in that the latter is, or was originally, a fixed and certain sum prescribed by statue for an offense; but an amercement is arbitrary. Hence, the act or practice of affeering. [See Affeer.] Blackstone. Note: This word, in old books, is written amerciament. Amercement royal, a penalty imposed on an officer for a misdemeanor in his office. Jacobs.