The imposition by a lord of a discretionary penalty; later the penalty itself. The greatest imposer of amercements was the king; they were a royal fine. *Magna Carta deals with such royal penalties. Thus, ch. 20 states of freemen: 'A free man shall be fined only in proportion to the degree of his offence, and for a serious offence correspondingly, but not so heavily as to deprive him of his livelihood.' Magnates were to be treated similarly in ch. 21: 'Earls and barons shall be fined only by their equals, and in proportion to the gravity of their offence.' [< AnNor. amercier, a merci = at (the) mercy (of another)]
Cf. previous
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.