Definition
A Law French adjective meaning "eldest" or "firstborn." The term appears in historical common law texts to designate seniority of birth, most often in the compound phrase bastard eigne — an illegitimate eldest child whose parents subsequently married and then had a legitimate child (called the mulier puisne). Eigne itself carries no independent legal doctrine; its significance lies entirely in the paired relationship with mulier puisne and the property consequences that followed from that pairing under old English land law.
Common Language
Modern common usage (Wiktionary): "Eldest; firstborn" and, secondarily, "entailed; belonging to the eldest son."
Historical common usage (Webster's 1913): "Eldest; firstborn" — illustrated directly by the legal compound bastard eigne, with the secondary sense of "entailed."
The common and legal meanings are largely coextensive here, but the secondary sense — "entailed; belonging to the eldest son" — reflects an old property usage that does not correspond to a free-standing legal doctrine. In legal sources, eigne almost never appears alone in a property context; the entailment sense is a derived inference from primogeniture rules rather than a term of art in its own right.
Common Confusion
Eigne and puisne are relational terms that only make sense together. Eigne marks the elder; puisne (or puisné) marks the younger or later-born. Researchers sometimes encounter puisne judge or puisne mortgage in modern sources and assume the word has shed its birth-order meaning. It has not — the core sense of "later" or "inferior in rank" persists, but the modern compounds no longer invoke family relationships. The confusion matters because a researcher tracing puisne through historical sources will find it tethered to eigne and the bastard eigne / mulier puisne doctrine, not to judicial or mortgage contexts.
Why It Matters in Research
Eigne is a fossil term — it does not appear in modern statutes or contemporary case law. Researchers encounter it almost exclusively when reading pre-nineteenth-century English materials on inheritance, legitimacy, and the effect of subsequent marriage on the status of an earlier-born illegitimate child.
The doctrine attached to bastard eigne had real property consequences: under certain historical rules, a bastard eigne who had long possessed land could defeat the later-born legitimate mulier puisne's claim, particularly if the mulier had acquiesced. The term therefore appears in discussions of seisin, adverse possession's predecessors, and the old writs governing land recovery. Finding eigne in a historical source is a reliable signal that the surrounding text is addressing legitimacy and its intersection with inheritance rather than eigne as an independent concept.
Because the term is Law French, it will not appear in early English-language statutes but will appear in treatise literature, Year Books, and digests. Littleton's Tenures (§ 399) and Blackstone's Commentaries (2 Bl. Comm. 248) are the canonical reference points. Any index search for eigne in digitized collections will return heavily clustered results from a narrow band of sources; absence from a source is not surprising and should not be taken as evidence that the doctrine was unknown to that author.
Researchers should also note that spelling varies across historical sources. Eigne, eigné, and the underlying French ainé all appear. Bouvier flags the term as a corruption of ainé; Black's (2nd Ed.) confirms this. Variant spellings can defeat full-text search if only one form is queried.
Historical Dictionary Support
All three source dictionaries agree on the core meaning — eldest or firstborn, Law French, a corruption of ainé — and all three anchor the term's legal significance in bastard eigne / mulier puisne. Black's (both editions) and Bouvier's point to Littleton § 399; Black's 2nd Ed. adds the Blackstone reference.
The dictionaries do not disagree with one another in any material way. What they collectively leave underdeveloped is the property doctrine itself: none of the entries explains why the distinction mattered — specifically, the rule that long possession by a bastard eigne could bar the mulier's claim. For that doctrinal substance, the dictionary entries function only as a pointer; the researcher must follow the citations to Littleton and Blackstone directly.
Webster's 1913 secondary sense ("entailed; belonging to the eldest son") is not developed in any of the legal dictionaries and appears to be a loose inference from primogeniture context rather than a recognized term of art. Legal researchers should not treat that secondary sense as authoritative.
Jurisdictional Note
Eigne is exclusively a term of English common law origin. American courts and statutes did not adopt it as an operative term, though early American treatise writers reproducing English common law doctrine occasionally quoted it. It has no independent doctrinal life in any American jurisdiction.