Definition
Un foitz is a Law French phrase meaning "one time" or "once." It appears in early English legal records and year books as a temporal qualifier, signifying that an act, event, or condition occurred or is to occur on a single occasion. The phrase is most commonly encountered in the maxim un ne doit prise advantage de son tort demesne — "one ought not to take advantage of his own wrong" — a principle of general application in equity and common law holding that a party may not benefit from their own wrongful conduct.
Common Language
The phrase has no meaningful modern common usage in English. As a Law French term, it belongs entirely to the technical vocabulary of early English legal proceedings and records.
Why It Matters in Research
Researchers encounter un foitz almost exclusively in medieval and early modern English year books and plea rolls, particularly those from the reign of Edward III (1327–1377) and surrounding periods. Its importance is less as a standalone term and more as a component of the maxim un ne doit prise advantage de son tort demesne, which survives in principle long after the Law French vocabulary that expressed it fell out of use.
Several research traps are worth noting. First, Law French spelling was highly inconsistent across scribes, courts, and centuries; un foitz may appear as un foiz, une foitz, or other variants depending on the manuscript tradition. Searches in digitized year book collections should account for this orthographic instability. Second, the substantive principle embedded in the maxim — that no party profits from their own wrong — reappears in later common law and equity doctrine under entirely different terminology (see RELATED TERMS below), meaning that a researcher tracing the doctrine's development must cross the terminological divide between Law French sources and later English and American materials. Third, the year book citation in Burrill (P. 6 Edw. III. 75) is a Plea term citation and requires familiarity with the conventional structure of Edwardian year book references to locate correctly.
Historical Dictionary Support
Burrill's Law Dictionary is the primary historical source for this entry and provides both a direct translation ("one time; once") and the associated maxim with citation. Burrill treats the term briefly, as is appropriate for a particle of Law French that functions chiefly as a qualifier. No substantive divergence exists across available historical sources because the term's range is narrow and its meaning unambiguous in context.
What historical dictionaries do not address is the downstream life of the principle expressed in the maxim. The rule that a party may not take advantage of their own wrong became a durable equitable and common law doctrine, appearing in later treatise literature and case law under formulations such as "he who comes into equity must come with clean hands" and the broader principle of ex turpi causa — though these are related rather than identical propositions. Researchers relying only on Law French dictionary entries will miss this doctrinal continuity.
Jurisdictional Note
As a Law French term, un foitz is historically specific to the English common law tradition. It has no independent existence in civil law, Scottish law, or American statutory systems, though the principle embedded in the associated maxim has been received into American equity jurisprudence through the general inheritance of English equitable doctrine.