Definition
A formal pledging of faith, fealty, or fidelity in medieval canon and feudal law. The term encompasses several related acts of solemn oath-taking or mutual faith-pledging between parties in a hierarchical or sacramental relationship. Three principal applications appear in historical legal sources:
1. Feudal fealty oath. The sworn act by which a person voluntarily placed themselves under a lord's protection, pledging faith and fidelity in exchange for that protection. The person taking the oath occupied a quasi-vassal position — not necessarily a full vassal by formal investiture, but someone who had voluntarily submitted to a lord's authority and assumed the reciprocal obligations that oath entailed.
2. Matrimonial faith-pledging (mutua affidatio). The mutual exchange of faith between husband and wife — the pledging of troth at the formation of the marital bond. This usage appears in Scottish legal sources, particularly Skene's De Verborum Significatione, and reflects the canon law understanding of marriage as grounded in a solemn mutual faith commitment.
3. Parliamentary oath (affidatio dominorum). An oath taken by lords in parliament. This institutional usage adapted the feudal concept of pledged faith into the context of parliamentary proceeding and obligation.
Common Language
This is a term of pure Latin legal and ecclesiastical vocabulary with no meaningful counterpart in modern or historical common English usage. The root concept — pledging or swearing faith — survives in English through related words such as "affiance" (to betroth) and "fidelity," but affidatio itself remained confined to legal and ecclesiastical Latin. The COMMON LANGUAGE section is omitted accordingly.
Why It Matters in Research
Affidatio is an archaic term that will appear almost exclusively in sources dealing with medieval feudal law, canon law, and early Scottish law. Researchers encounter it most often when working with:
— Feudal tenure and homage materials. Affidatio overlaps with, but is distinct from, homage (homagium) and fealty (fidelitas). Distinguishing these acts matters when tracing the precise legal obligations created by a given historical ceremony. Affidatio often denotes the oath component specifically, whereas homage was a broader ceremonial act of submission.
— Scottish legal sources. Skene's De Verborum Significatione and Regiam Majestatem are primary carriers of this term in the Scottish legal tradition. Researchers working in early Scots law should expect affidatio to carry the matrimonial faith-pledge meaning more prominently than English sources typically reflect.
— Canon law materials. The canon law tradition used affidatio in connection with both marriage formation and clerical oath obligations. Spelman's Glossarium Archaeologicum is the principal reference source cited by historical dictionaries on this term and is worth consulting directly for nuanced usages.
— Parliamentary records. The affidatio dominorum form of the oath has implications for research into the historical obligations of peers and the nature of parliamentary membership in early English constitutional history.
The term does not generate modern litigation or statutory research. Its research value is entirely historical and documentary.
Historical Dictionary Support
The three source dictionaries present a consistent core definition with useful supplementary detail. Black's (both editions) gives the lean formulation: a swearing of the oath of fidelity or fealty to one's lord by one who has voluntarily come under that lord's protection, attributing the definition to Brown. This formulation captures the feudal fealty meaning clearly but omits the matrimonial and parliamentary dimensions.
Burrill's is the more complete entry and provides the most useful research footing. Burrill draws on Spelman directly and introduces the mutua affidatio — the mutual faith-pledging between husband and wife — citing Skene's De Verborum Significatione. This is an important addition absent from Black's, and researchers working in canon or matrimonial law contexts should not rely on Black's alone.
All three sources share Spelman as a common authority, and Bracton (fol. 88a) appears in Burrill for the fealty oath meaning — a useful reference point for researchers needing a primary medieval source.
None of the dictionary sources treat affidatio dominorum at length; Black's 2nd Ed. notes it as a sub-entry without elaboration. Researchers needing detail on the parliamentary oath form will need to look beyond these dictionaries to parliamentary records and constitutional histories directly.
Jurisdictional Note
Affidatio appears most prominently in English feudal law sources and early Scottish law. The matrimonial usage is particularly associated with Scottish legal tradition through Skene and Regiam Majestatem. In continental canon law, parallel concepts exist under related terminology. No modern jurisdiction employs the term in active legal practice.