A more thorough explanation:

Affidatio dominorum was a legal term used in Latin. It refers to an oath taken by lords in Parliament.

During the medieval period, lords in Parliament would take an affidatio dominorum to swear their loyalty to the king and to uphold the laws of the land.

For example, in 1215, King John of England was forced to sign the Magna Carta, which was a document that limited the power of the king and protected the rights of the people. The lords who were present at the signing of the Magna Carta would have taken an affidatio dominorum to show their support for the new laws.

These examples illustrate how affidatio dominorum was an important part of the legal system in medieval England. It was a way for lords to publicly declare their loyalty to the king and to show their commitment to upholding the laws of the land.