Definition
A term of evidence and documentary law applied to a signature that is written in a different hand from the body of the instrument it authenticates. An onomastic signature is not unusual or necessarily suspect — it was historically common for a party to sign a document drafted or copied out by a scrivener, clerk, or notary, resulting in two distinct handwriting styles appearing in the same instrument. The term flags this circumstance as a recognized condition requiring attention in the analysis of documentary authenticity.
Common Language
Modern common usage (Wiktionary): Of or relating to a personal or place name; of or relating to onomastics (the study of names).
Historical common usage (Webster's 1913): Applied to a signature when the body of the instrument is in another's handwriting.
The gap here is significant and runs in an unexpected direction. In modern general usage, "onomastic" is an adjective rooted in linguistics and name studies — it has nothing to do with handwriting. In its narrow legal meaning, the word is almost never used outside the evidence and authentication context. A researcher encountering "onomastic" in a general linguistic or scholarly text should not assume any legal document-authentication meaning is intended, and vice versa.
Common Confusion
Onomastic should not be confused with holograph or holographic, which describes an instrument written entirely in the hand of the person signing it — the opposite condition. An onomastic instrument is precisely one that is not holographic: the body is in one hand, the signature in another. Some researchers also conflate onomastic with allographic (written by another for the signer), but allographic emphasizes the body of the text written by a third party, while onomastic specifically foregrounds the signature as the analytically distinct element.
Why It Matters in Research
Researchers working in historical evidence law, authentication disputes, or pre-modern document analysis may encounter this term in treatises and will not find it in modern statutory or procedural codes — it fell out of active legal usage and survives primarily as a period term in evidentiary writing.
Two research traps arise. First, the corpus of sources citing this term is narrow: the primary authorities are William Best's treatise on evidence (Best, Ev.) and Jeremy Bentham's Rationale of Judicial Evidence (2 Benth. Jud. Ev.). Both are 19th-century English works. The term as a legal term of art is largely English in origin and only occasionally appeared in American legal writing. Burrill's entry, notably, drifts from the standard definition and partially conflates the discussion with insurance policy forms — a signal that even historical compilers were uncertain of the term's precise scope.
Second, the divergence between Burrill and the other historical dictionaries is itself a research signal. Burrill's entry gestures toward American usage but connects "onomastic" to insurance forms using the phrase "for whom it may concern," a slip that appears to conflate separate doctrinal discussions. Researchers relying solely on Burrill for this term may be misled.
For corpus researchers: when this term surfaces in historical legal documents, it marks a specific evidentiary concern — whether a document's authenticity can be established when the handwriting of the body and signature cannot be matched to a single hand. This bore on proof of execution, forgery detection, and the competency of instruments in probate and commercial contexts.
Historical Dictionary Support
Black's (1st and 2nd editions) and Bouvier agree cleanly on the definition: the term describes a signature in a hand different from the body of the instrument. Both cite Best on Evidence as the primary source, with the 2nd edition citing page 815 and the 1st citing page 315 — a discrepancy likely reflecting different editions of Best's treatise. Bouvier adds the Bentham citation (2 Benth. Jud. Ev. 460), which situates the term in the utilitarian evidence-reform tradition of the early 19th century.
Burrill is the outlier. His entry acknowledges the Greek root (ónoma, name) and briefly states the standard meaning but then pivots to a discussion of American insurance policy forms, connecting "onomastic" to open policies and the "for whom it may concern" clause. This connection does not appear in other sources and is likely an editorial conflation rather than an established secondary meaning. Researchers should treat the Burrill entry with caution and cross-check against Best and Bentham directly.
What all four sources miss: no dictionary entry addresses the evidentiary consequences of an onomastic instrument in specific procedural terms — what presumptions attached, what proof was required to authenticate such a document, or how courts actually treated the condition at trial. For that analysis, researchers must go to the primary treatise sources.
Jurisdictional Note
The term appears to have been more current in English legal practice and treatise writing than in American courts. American adoption was limited and inconsistent, as Burrill's uncertain entry suggests. Researchers should not expect to find "onomastic" as a recognized term of art in American state court opinions or codes.