Definition
An ancient customary formality by which a bargain or contract was sealed between parties. The act consisted of the parties licking their thumbs and pressing them together — or some variation of that gesture — as a physical token of mutual assent and agreement. The gesture functioned as the equivalent of a handshake, a seal, or a signature in more formal legal contexts: it marked the moment at which the parties considered themselves bound.
The licking of thumbs belonged to a category of informal oral and gestural contract formation practices that preceded widespread literacy and the standardization of written instruments. It was not a creature of statute but of custom, recognized in legal literature as evidence that parties had concluded their dealing.
---
Common Language
Modern common usage (Wiktionary): Not independently listed as a standard entry; the phrase appears primarily in historical and literary contexts, most famously in Shakespeare's Romeo and Juliet, where biting one's thumb is used as an insult — a distinct and opposing gesture.
Historical common usage (Webster's 1913): Not separately defined; the phrase would have been understood as a folk or trade custom associated with market dealings and the conclusion of bargains, particularly among merchants and at fairs.
The gap worth noting: the common literary association of thumb-related gestures runs toward provocation or insult (biting the thumb), while the legal usage points in the opposite direction — toward consent and completion. A researcher encountering the phrase in a historical legal source should not import the adversarial connotation; the legal meaning is one of affirmation and mutual commitment.
---
Why It Matters in Research
Researchers are unlikely to encounter this term in operative legal documents or modern case law. Its significance is historical and contextual: it appears in legal dictionaries as a window into pre-modern contract formation, where the law recognized a variety of physical customs — beyond written seals or signatures — as sufficient to complete an agreement.
For researchers working in early English commercial law, market customs, or the history of contract formation, this term connects to the broader problem of how informal agreements were recognized and enforced before the formalization of contract doctrine in the seventeenth and eighteenth centuries. It sits alongside thumb-printing, handshakes, earnest money, and the striking of hands (arles) as markers of completed oral bargains.
The term also illustrates a gap in historical legal dictionaries: both Black's editions define it in a single clause, with no supporting authority, no jurisdictional grounding, and no indication of when or where the custom was actually practiced or litigated. Researchers should treat both entries as antiquarian observations rather than doctrinal statements. Neither edition cites a case, statute, or treatise to anchor the definition, which means the legal weight of the custom is essentially unverifiable through those sources alone.
If encountered in a primary source — a market record, a pleading, or a chronicle — the term should be read as evidence of informal assent, but the researcher must independently establish the jurisdiction, period, and legal context to determine what evidentiary or binding force it would have carried.
---
Historical Dictionary Support
Both Black's editions are in complete agreement and are nearly identical in wording: the licking of thumbs was "an ancient formality by which bargains were completed." Neither edition elaborates, cites authority, or explains the mechanism by which this formality was recognized in law. The brevity itself is informative — the editors treated the term as a historical curiosity meriting acknowledgment but not sustained analysis.
What the historical dictionaries miss: any discussion of the relationship between this custom and the law of assumpsit, the role of consideration, or the question of whether such a gesture could serve as evidence of a completed contract in a court of law. They also do not situate the custom geographically or chronologically — whether it was a specifically English practice, a broader European one, or a survival from even earlier customary law is left entirely open.
Researchers should not treat Black's inclusion of this term as evidence that it carried significant doctrinal weight in any particular legal system. It appears to have been preserved in legal dictionaries as a record of folk practice at the boundary of law and custom.
---