Definition
A castellan; the keeper or constable of a castle. In medieval feudal law, the oastellanus was the officer charged with the custody, defense, and administration of a castle, typically holding that position by appointment from or grant of a lord or the crown. The term functions as a variant spelling of castellanus and carries the same legal and administrative meaning.
Why It Matters in Research
This term appears only in the supplemental materials of Black's 2nd edition and is drawn from Spelman's glossary of Latin legal and feudal terms — a signal that researchers will encounter it almost exclusively in medieval land records, feudal tenure documents, and early English legal manuscripts rather than in modern case law or statute. The unusual initial "O" in place of the expected "C" reflects either a scribal variant or a copyist's rendering of manuscript Latin, and researchers searching historical sources should search for both spellings: oastellanus and castellanus. The two forms index to the same office and the same body of feudal law.
The practical significance of the oastellanus in legal history lies in questions of custody and authority: who held a castle determined who controlled the surrounding territory, exercised local jurisdiction, and bore obligations to the lord above. Researchers working in English feudal tenure, inquisitions post mortem, or early common law records touching on castle-guard tenure (a distinct feudal service obligation tied to castle defense) should treat this term as a gateway to the broader castellanus literature. Do not expect to find the "oastellanus" spelling replicated in primary sources — it is essentially a lexicographical artifact of how the term was transcribed into Black's supplemental glossary.
Historical Dictionary Support
Black's Law Dictionary (2nd ed., Supplemental) provides a one-line entry: "A castellan; the keeper or constable of a castle. Spelman." The attribution to Spelman refers to Sir Henry Spelman's Glossarium Archaiologicum, the foundational glossary of archaic legal and feudal Latin terms, which remains an essential reference for medieval English legal vocabulary. Black's entry does not expand on the duties, tenure conditions, or legal incidents of the office beyond the bare identification — a common limitation of the supplemental glossary entries, which function as vocabulary aids rather than substantive legal analyses.
Spelman's treatment of castellanus in the Glossarium is more expansive, addressing the feudal relationship between the castellan and the lord, the nature of the custody, and the distinction between hereditary castellans and those appointed at will. Researchers needing substantive content on the office should consult Spelman directly rather than relying on Black's compressed reference. No other standard historical law dictionary in the Law Mind corpus appears to carry an independent entry under the "oastellanus" spelling; coverage of this concept in other sources (such as Bouvier's) appears under castellan or constable rather than the Latin form.
Jurisdictional Note
The office of oastellanus or castellanus is a creature of English and Continental feudal law with no surviving counterpart in modern American or English legal systems. Research relevance is confined to historical English law, medieval land tenure, and the feudal period preceding and immediately following the Norman Conquest.