Definition
Eignty is an archaic legal term denoting the condition or status of being the eldest — specifically, the right or quality of eldership as it pertains to inheritance. It describes the priority claim of a firstborn child, particularly an eldest son, to an inheritance or estate under the rules of primogeniture. Where two persons claim the same land or inheritance by descent, eignty refers to the superior title held by the elder claimant by virtue of birth order.
The term is most closely associated with the phrase "bastard eigne" (bastard elder) and "mulier puisne" (legitimate younger), a specific common law doctrine governing competing inheritance claims between an illegitimate firstborn and a legitimate later-born child of the same father.
Common Confusion
Eignty is occasionally confused with sovereignty due to phonetic similarity and the data artifact described above. The two terms have no legal relationship. Sovereignty concerns supreme political authority of a state; eignty concerns birth-order priority in private inheritance law. Researchers should also distinguish eignty from seniority in the general sense — eignty is a technical term of the law of descent, not a general descriptor of age or rank.
Why It Matters in Research
Researchers encountering eignty in historical sources will almost always find it embedded in the bastard eigne / mulier puisne context, not as a standalone concept. The doctrine addressed a narrow but important fact pattern: a man has a child out of wedlock (the bastard eigne), then marries the mother, and later has another child within the marriage (the mulier puisne). At common law, if the father died and the bastard eigne had been in open possession of the land without challenge during the father's lifetime, the bastard's title through eignty could, in certain circumstances, defeat the legitimate child's claim.
This makes eignty a term of art in medieval and early modern English land law. It will surface in readings on primogeniture, descent and distribution, and the law of bastardy. Researchers working in American colonial law should note that the bastard eigne doctrine had limited reception in American jurisdictions, where statutory reforms to inheritance and legitimacy displaced these common law distinctions early. The term is unlikely to appear in American case law after the nineteenth century except as historical reference.
The Black's Law Dictionary source material provided here contains a definition that does not match the term as it appears in the historical record. The definition given — "that power in a state to which none other is superior or equal" — is the definition of SOVEREIGNTY, not eignty. This appears to be a transcription or extraction error in the source data. Researchers should be alert to this kind of data artifact when working with digitized or algorithmically processed legal dictionary corpora. The entry for eignty in Black's properly concerns the law of primogeniture and birth-order priority, not sovereign power.
Historical Dictionary Support
Black's Law Dictionary has historically treated eignty in the context of bastard eigne, connecting it to the common law rules governing illegitimacy and inheritance priority. The term derives from the Old French "aîné" (eldest) and was fully naturalized into English legal vocabulary by the medieval period. Historical dictionaries largely agree on the core meaning: eignty marks the quality of being elder-born and the legal consequences that flow from that status in a property dispute.
What historical sources sometimes obscure is the contingent nature of the eignty claim — it was not an absolute trump. The bastard eigne's title through eignty only prevailed under specific conditions, particularly where possession had been long and uncontested and the mulier puisne had failed to assert a timely claim. Modern legal dictionaries have largely dropped eignty as an active entry, reflecting its obsolescence in jurisdictions that have abolished primogeniture and reformed the law of bastardy.