In the Anglo-Saxon and Norman periods, a money penalty imposed on an offender in the court of his lord. The word comes from the Norman French 'a merci', at the mercy of the court or king, for the amount of an amercement was originally arbitrary and a fruitful source of income for a lord. It became gradually fixed in many cases, and in others Magna Carta (1215) stipulated that a freeman should be amerced according to his means. Amercements gradually gave way to fines. HISTORY.