The American Heritage English Dictionary has this to say of the term:
The courtroom cry "Oyez, oyez, oyez," has probably puzzled more than one auditor, especially if pronounced "O yes." (Many people have thought that the words were in fact "O yes.") This cry serves to remind us that up until the 18th century, speaking English in a British court of law was not required and one could instead use Law French, a form of French that evolved after the Norman Conquest, when Anglo-Norman became the language of the official class in England. Oyez descends from the Anglo-Norman oyez, the plural imperative form of oyer, "to hear"; thus oyez means "hear ye" and was used as a call for silence and attention. Although it would have been much heard in Medieval England, it is first recorded as an English word fairly late in the Middle English period, in a work composed around 1425.
Yes, French was the language of choice in English Courts for a good number of years. It wasn't until the Statute of Pleading was passed in 1362 that English was permitted to be used by litigators. Though the statute became law, the use of french was still permitted, and documents were often filed with the court in french for at least three centuries after the passage of this statute.
Most statutes during that time were also written in french as an early Arms Control Act from 1383 shows.
If you read through the Many Variations of Trial by Combat, which is a description from Thomas, the Duke of Gloucester and constable under Richard II, on the Manner of Conduction of Judicial Duels, you'll see the use of "oyez, oyez, oyez" to begin a trial by combat (from Medieval Life & The Hundred Years War).
From the enlightening article Plain Language--The Arrows in Our Quiver, we find some other words that were derived from this use of french in English courts, including: action, appeal, attorney, claim, complaint, counsel, court, defendant, evidence, indictment, adjudge, judgment, jury, justice, parol, party, plaintiff, plea, sentence, sue, summon, and voir dire.
Will terms like "oyez, oyez, oyez" continue to be part of our legal system? The Statute of Pleadings was intended to allow the people being represented in court the opportunity to understand what was being said during legal proceedings. Plain english language used in courtrooms and legal documents today would go a long way towards the same result. But the tradition recitation of oyez three times will probably continue on as part of the historic tradition of the courts.
(Any discussion of the use of the term "oyez" should also point towards one of the best resources on the web about the US Supreme Court, which is the Oyez Project from Northwestern University.)
- William Slawski