The term "affeer" is no longer used in law and, if it were, lawyers' brains would revert to pre-law-school mush trying to figure out what it means.

Affeer has two distinct meanings, oddly enough.

When Shakespeare uses it in Macbeth (IV.3)...

Bleed, bleed, poor country!
Great tyranny! lay thou thy basis sure,
For goodness dare not cheque thee: wear thou
thy wrongs;
The title is affeer'd! Fare thee well, lord:
I would not be the villain that thou think'st
For the whole space that's in the tyrant's grasp,
And the rich East to boot.

... he uses it to mean "assured" or "secured."

The Common Law meaning was quite different. At Common Law, there were three amounts of money which a court (or crown) might require a subject to pay: damages, fines and amercements.

Damages arose from a civil lawsuit in which one party proved that another party had damaged it or its interests, which damage was then compensated by requiring the damaging party to pay damages.

Fines arose from misdemeanors where, if it could be shown that a subject did a prohibited thing, a specified amount of money could be required of the offending person, which amount was paid to the crown (or lord) for the insult/injury to the majesty's dignity.

Amercements were monetary penalties imposed by a court for misdemeanors where no amount was specified by statute, thus the court was permitted, in a sense, to make up the penalty. One was at the court's (or crown's or lord's) mercy and thus the term amercement.

The act of imposing, in the first instance, or amending, on appeal, an amercement was called affeering or affeerment or some such term.

We don't do a lot of that in the 21st Century Colonies, but there are parallels to this antecedent of imposing civil penalties for minor wrongs, e.g. variable fines for traffic violations (sometimes called infractions) which do not constitute crimes.