Definition
A tun is a traditional unit of liquid measure equal to four hogsheads, used historically to quantify wine, oil, and other liquids in legal instruments, taxation schedules, customs records, and trade documents. In English commercial and statutory practice, four hogsheads constituted one tun, though the precise gallon-equivalent varied by commodity and period; the most commonly cited standard is 252 wine gallons.
The term also appears in older English place-name law and land terminology. Burrill records tun (from the Saxon, rendered in Low Latin as tuna) as a word for a farm or rural estate — a meaning that survives today only as the suffix -ton in English town and place names. This second sense is purely historical and has no active legal application.
Common Language
Modern common usage (Wiktionary): A large cask, oblong and hooped; a fermenting vat; a traditional liquid measure of 252 wine gallons or 2 pipes; loosely, a synonym for long ton (2,240 pounds).
Historical common usage (Webster's 1913): A large cask for wine or other liquids; a fermenting vat; a liquid measure equal to two pipes, four hogsheads, or 252 gallons, varying by country; occasionally used for a weight of 2,240 pounds (see ton); and informally for an indefinitely large quantity.
The common usage and legal usage are closely aligned when tun refers to the liquid measure or the cask itself. The meaningful gap lies in what the law fixes and what common usage leaves flexible: legal instruments and customs schedules treated the tun as a defined unit with specific fiscal and trade consequences, while everyday usage tolerated considerable variation in its exact quantity. Researchers should also note that common usage preserves the weight sense (tun as ton) entirely absent from the legal definitions.
Common Confusion
Tun, pipe, hogshead, and butt are a nested family of cask-based liquid measures that appear throughout the same historical sources and are easily conflated. The standard relationship is: 1 tun = 2 pipes (or butts) = 4 hogsheads. A pipe and a butt are near-equivalent measures of approximately 126 gallons each; a hogshead is approximately 63 gallons. These ratios held as a general rule in English law, but actual volumes differed by commodity (wine, beer, oil) and by jurisdiction. Do not assume a hogshead of beer equals a hogshead of wine — they do not. When reading historical customs or excise records, always identify the commodity before applying a gallon equivalent to any of these terms.
Tun should not be confused with ton, though the two words share a common origin and Webster's 1913 treats them as occasionally interchangeable. In legal and commercial records, tun is the liquid measure; ton is the weight measure.
Why It Matters in Research
Tun appears most often in three research contexts: (1) historical customs and excise law, where duties were assessed per tun of wine or oil imported; (2) commercial contracts and conveyances involving the sale or storage of liquids in bulk; and (3) English land and local history, where the Saxon tun underlies place-name suffixes that appear in property descriptions and jurisdictional boundaries.
For corpus researchers, the key trap is assuming consistency of measurement. The tun as a legal unit was more stable than the tun as a common commercial term, but even legal sources reflect variation across time and commodity. Sixteenth- and seventeenth-century English statutes and customs schedules frequently specify tuns of wine with a particular gallon count; do not transpose that count to tuns of oil or beer without verification.
The place-name sense (tun as farm or settlement) surfaces in Burrill but not in Black's or Bouvier's, reflecting Burrill's greater attention to Anglo-Saxon and Low Latin terminology. Researchers working on early English land records or borough charters may encounter this sense where the other dictionaries offer no guidance.
The term has essentially no active role in modern American law. Its research value is almost entirely historical — English trade law, colonial-era customs records, and early American commerce statutes that carried forward English measurement conventions.
Historical Dictionary Support
All four historical dictionaries agree on the core legal definition: a tun is a liquid measure containing four hogsheads, used for wine and oil. Black's (both editions) and Bouvier's give identical, minimal entries — a single sentence each — suggesting the term was treated as settled and unremarkable by the time those dictionaries were compiled.
Burrill is the outlier. His entry for tun branches in two directions: it records the liquid-measure sense only implicitly (the entry trails into an adjacent term, Turba), while devoting more attention to the Saxon etymological sense of tun as a farm or settlement (prædium, villa) distinguished from ham (a chief house or mansion). This is genuinely useful information that the other dictionaries omit entirely, and it reflects Burrill's broader historical methodology compared to Black's and Bouvier's more practice-oriented approach.
None of the historical dictionaries specify a gallon equivalent, which is where researchers are most likely to need precision. For that, statutory sources and specialized works on historical weights and measures are necessary supplements.
Jurisdictional Note
The tun as a legal unit of measure is a feature of English law and early Anglo-American commercial and customs practice. It does not appear as an operative unit in modern American statutory or regulatory frameworks. Researchers working on colonial American records will encounter English measurement conventions carried over directly; variation from those conventions is worth flagging when found.