You will likely have heard people say that something has taken place “since time immemorial.” It’s such a familiar phrase that it’s almost become a cliche—used to describe anything particularly ancient, well-established, aged, or longstanding.

The word immemorial itself essentially means “unrememberable,” or literally “beyond all memory.” The term time immemorial, ultimately, describes any period beyond that which can easily or accurately be recalled by people alive today. But that fairly imprecise definition isn’t the only definition of this curious phrase recorded in the dictionary. In fact—in legal contexts in particular—the expression time immemorial quite literally, and very specifically, refers to any time before July 6, 1189.

So why does such a specific meaning exist? And where on earth does it come from?

In legal contexts, the concept of time immemorial was originally introduced to British statute law, during the reign of King Edward I in the late 13th century. King Edward oversaw the introduction of three influential directives collectively known as the Statutes of Westminster. This was a trio of formal legal documents that attempted to codify all the laws of England, and thereby establish a new and fully comprehensive English legal system in writing for the very first time. (Ironically, despite establishing the foundations of much of the legal system that still survives in England today, all three of these documents were originally written in French!)

The first of these Statutes was compiled in 1275 and defined all manner of important legal concepts like slander, electoral freedom, and ‘Acts of God’. And Clause 39 of this first Statute, — officially titled “The Limitation of Prescription Act”; sought to define a standardized cut-off point for assessments of legal ownership.

“No one is to be given a hearing to claim seisin,” the document stated, “by any ancestor of his further back than the time of King Richard, uncle of King Henry, the father of the present king.” (Seisin being an old name for feudal ownership of land.)

In other words, Clause 39 of the First Statute of Westminster implied that if you ever had your ownership of a given property or plot of land legally challenged, all you had to do to quash the challenge was prove that you and your ancestors had maintained ownership of that property since before King Richard I, (Edward I’s great uncle) had ascended to the throne. King Richard’s ascendancy took place on 6 July, 1189, and ultimately, it was this date that was established as the legal cut-off point for living memory. Anything that occurred before that date was therefore deemed to be beyond living memory—or, in legal parlance at least, ‘time immemorial’.

Incredibly, this definition remained in force in England right through to 1832, when it was finally decided that being legally compelled to demonstrate personal ownership of something for 643 years could prove somewhat difficult! As a result, in 1832 the King of England, William IV (the uncle of Queen Victoria, who succeeded him five years later), passed the so-called Prescription Act, which shortened the legally required length of ownership for use of a contested property to anything from 20 to 60 years, depending on the type of property in question.

As for ‘time immemorial’, it came to be used more loosely as an expression over time, becoming just another word for an inexpressibly long duration. But its original meaning—thanks to some obscure legal jargon, and a little bit of help from King Richard I; was originally a great deal more specific than that.