Definition
An oath taken by the lords in parliament. The term is Latin, translating roughly as "the sworn pledge of the lords," and refers to the collective oath of allegiance or fidelity administered to members of the House of Lords in the English parliamentary tradition. It reflects the feudal structure of parliamentary obligation, in which the lords' participation in parliament was understood not merely as a privilege of rank but as a duty underwritten by formal oath.
Why It Matters in Research
This is a narrow historical term with no living legal application. Researchers encountering it will do so almost exclusively in primary sources from medieval and early modern English law — parliamentary records, treatises on constitutional history, or works on feudal tenure and obligation. Its significance is contextual: it illuminates the oath-bound character of early parliamentary membership and the degree to which feudal concepts of fealty structured formal governmental institutions.
Researchers working in English constitutional history should note that the affidatio dominorum belongs to a cluster of oath-related terms and procedures — including the oath of supremacy and the oath of allegiance — that underwent significant statutory transformation across the sixteenth and seventeenth centuries. The affidatio dominorum as a distinct procedural form predates that period and may not appear under a consistent label across different chronicle or parliamentary sources. Do not expect uniformity of usage.
The term has no American legal analog. It will not appear in domestic U.S. sources except as a reference term in comparative or historical scholarship.
Historical Dictionary Support
Black's Law Dictionary and Rapalje & Lawrence are in complete agreement: both define affidatio dominorum as "an oath taken by the lords in parliament," with no elaboration. Neither source contextualizes the oath within the broader development of parliamentary procedure, nor distinguishes it from related oath forms. This convergence likely reflects shared derivation from a common Latin legal glossary tradition rather than independent research by either editor.
What the historical dictionaries omit is notable. They do not identify when the practice arose, under what circumstances it was administered, whether it was a single uniform oath or varied by occasion, or how it related to the general feudal concept of affidatio (sworn fealty between lord and vassal). Researchers seeking substantive treatment should look beyond law dictionaries to works on English parliamentary history and medieval constitutional law, where the oath structure of early parliaments is examined in greater depth.
Jurisdictional Note
Strictly English in origin and application. The term has no reception in American, Scottish, or Irish legal traditions as a term of art. It appears in legal dictionaries of American and English law solely for historical completeness.