Origins
The English word 'perjury' entered the language in the late fourteenth century from Anglo-Norman French 'perjurie,' which came from Latin 'periūrium,' meaning a false oath or oath-breaking. The Latin word is composed of 'per-' (in this case meaning away from, deviating from, or destructive of) and 'iūrāre' (to swear an oath), itself derived from 'iūs, iūris' (law, right, that which is binding). The PIE root is *h₂yew-, which carried the sense of sacred law or binding force — the kind of law that was considered divinely ordained rather than humanly enacted.
The prefix 'per-' in 'perjury' is often misunderstood. In many Latin words, 'per-' means 'through' or 'thoroughly' (as in 'perfect,' 'perceive,' 'permeate'). In 'periūrus,' however, it carries the less common meaning of 'away from' or 'to the detriment of' — the same sense found in 'perish' (to go through to destruction) and 'perdition' (total loss). A perjurer is someone who has 'sworn away' from the truth — their oath is not merely incomplete but actively destructive of the legal order that oaths are meant to uphold.
The root 'iūs' is one of the most important in Western legal vocabulary. From it derive 'jury' (a body of people sworn to give a verdict), 'just' (conforming to law or right), 'justice' (the administration of law), 'jurisdiction' (the area within which law is administered, literally 'law-speaking'), 'jurisprudence' (the philosophy of law, literally 'law-wisdom'), 'jurist' (one learned in law), and 'judge' (from Latin 'iūdex,' literally 'law-pointer'). All of these words share the concept that law and swearing are fundamentally connected — that the legal system rests on the sanctity of the sworn word.
Latin Roots
Perjury was considered one of the most serious offenses in both Roman and medieval law. In Roman practice, the oath (iūrāmentum) invoked the gods as witnesses, and breaking it was an offense against divine as well as human order. Roman law punished perjury with infamia — a formal declaration of dishonor that stripped the offender of legal rights. In medieval English common law, perjury was punished with imprisonment, fines, and sometimes the pillory. The severity of the punishment reflected the understanding that the entire legal system depends on witnesses telling the truth: if oaths mean nothing, courts cannot function.
The English common law distinction between perjury and related offenses is precise. Perjury requires that the false statement be made under oath, in a judicial proceeding, on a matter material to the case, and with knowledge that the statement is false. A lie told outside court is not perjury. A mistaken statement honestly believed is not perjury. An irrelevant falsehood, even under oath, may not constitute perjury. This narrow definition reflects the law's concern with the institutional integrity of the oath rather than with lying in general.
The related offense of 'subornation of perjury' — persuading someone else to commit perjury — uses the Latin prefix 'sub-' (under, secretly) + 'ornāre' (to equip, to furnish), literally meaning 'to secretly equip' someone to lie. The vocabulary of perjury law is thoroughly Latin, reflecting the Roman origins of the Western legal tradition.
Semantic Evolution
Other words from the 'iūrāre' family illuminate the deep connections between swearing and social order. 'Abjure' (to swear away, to renounce under oath) was used when heretics or traitors formally repudiated their beliefs or allegiances. 'Adjure' (to swear toward, to solemnly charge) was used to compel testimony. Most surprisingly, 'conjure' derives from 'coniūrāre' (to swear together), originally meaning a conspiracy sealed by mutual oaths; the magical sense — summoning spirits — developed because magic was understood as compelling supernatural beings through the power of sworn words and sacred names.
German uses 'Meineid' for perjury, from 'mein' (false, treacherous) + 'Eid' (oath) — literally 'false oath.' The Germanic approach is more transparent than the Latin, but both arrive at the same concept: an oath that has been corrupted. In both traditions, the violation of a sworn word is not merely a lie but an attack on the foundation of social trust.