Definition
A Latin term used in old English law with two primary meanings:
1. A sack or bag, specifically a standard unit of measurement for wool. A saccus represented a quantity of wool weighing either twenty-eight or thirty stone, depending on the authority consulted. Two ways (weys) made a sack, and twelve sacks constituted a last — establishing saccus as a fixed point in a hierarchy of commercial weights used in the medieval wool trade.
2. A sack, pack, or pack-saddle in the more general sense, appearing in medieval household and estate records to describe bundled goods or the means of transporting them.
Common Language
Modern common usage (Wiktionary): In modern English, "saccus" appears primarily as a botanical and palynological term — a bladder or winglike structure on pollen grains of conifers, used in species identification.
Historical common usage (Webster's 1913): Listed simply as a variant form of "sac," meaning a pouch or bag-like anatomical structure.
The gap between common and legal meaning is complete. The legal term is a medieval Latin commercial unit with no connection to botany or anatomy. A researcher encountering saccus in an old English legal or estate record should not expect any overlap with the term's modern scientific usage. The shared Latin root (bag, sack) is the only thread connecting them.
Why It Matters in Research
Saccus matters primarily to researchers working in medieval English commercial law, wool trade regulation, and manorial or household accounting. The wool trade was one of the dominant sources of English crown revenue from the thirteenth through the fifteenth centuries, and saccus appears in records of customs, staple regulations, and estate compoti precisely because standardized measurement units were legally significant — disputes over weight and measure had direct fiscal and contractual consequences.
The weight discrepancy among authorities is a genuine research trap. Black's gives twenty-eight or thirty stone; Burrill gives the same range but adds Cowell's figure of twenty-six stone. A researcher relying on a single source to reconstruct a quantity from a historical record may arrive at materially different figures. When precision matters — for example, in reconstructing customs duties owed or cargo quantities in a dispute — all available contemporary sources for the specific jurisdiction and period should be consulted.
The abbreviation problem: Black's notes that "s.v." (sub voce) is sometimes abbreviated as a form of saccus in older references. While unlikely to cause serious confusion in context, researchers using legal abbreviation tables should be alert to this overlap in heavily abbreviated manuscript or early print sources.
Burrill's reference to the Bolton Priory compotus (a household account book) signals that saccus appears not only in formal legal instruments but also in estate management records. Researchers working with ecclesiastical or manorial archives from northern England may encounter the term in administrative rather than strictly legal contexts.
Historical Dictionary Support
Black's and Burrill's agree on the core definition and both cite Fleta, the late thirteenth-century legal treatise, as the primary authority — specifically lib. 2, c. 79, § 10 for the wool-weight definition, and lib. 2, c. 12, § 2 for the sack-wey-last hierarchy. Burrill adds the Cowell variant (twenty-six stone) and provides the additional meaning of pack or pack-saddle from Fleta lib. 2, c. 21, which Black's omits.
Neither historical dictionary engages with the broader context of wool staple law or the administrative machinery that gave standardized wool measurement its legal force. For that context, researchers should look beyond the dictionary entries to treatise literature and the records of the wool staple system. The Latin dictionary tradition (Lewis and Short) confirms the classical Latin meaning of saccus as simply a sack or bag, and specifically a money-bag, which underscores that the technical commercial meaning in English law is a medieval development layered onto a common Latin word.
Jurisdictional Note
Saccus as a legal term of measurement is specific to medieval English law, particularly in the context of the wool trade and royal customs administration. It does not carry this technical meaning in Continental legal systems, though analogous measurement units appear in other European commercial law traditions under different names.