There are a lot of things that I'm curious about and one of them happens to be common phrases we use without knowing the origin and true meaning of said phrase.
Have you ever heard anyone, especially a posh British actor utter the words "time immemorial"? What does it mean and where did it come from? I never really thought about this before until it was brought up in an episode of QI, hosted by Stephen Fry. I would highly recommend this show to anyone who wants to educate themselves about the world: the obscure, the absurd, the incorrect and the fascinating are revealed.
When people used the phrase 'time immemorial' they may think it means back in the mists of time, before recorded memory when in actual fact the phrase is attached to a real date.
Wikipedia says English law define the phrase as 'time out of mind', 'a time before legal history and beyond legal memory'.
In the year 1275 at the Statue of Westminster where existing English law was codified the phrase was given meaning. The men at the the Statute said 'time of memory' was limited to the reign of Richard I, whose first day as king was July 6 1189 when he acceded the throne. And then there's a whole bunch of legal mumbo jumbo.
Wikipedia: Since that date, proof of unbroken possession or use of any right made it unnecessary to establish the original grant under certain circumstances. In 1832, time immemorial was re-defined as "Time whereof the Memory of Man runneth not to the contrary." The plan of dating legal memory from a fixed time was abandoned; instead, it was held that rights which had been enjoyed for twenty years (or as against the Crown thirty years) should not be impeached merely by proving that they had not been enjoyed before (holding by adverse possession).
Here's another great example from the perfectly cantankerous David Mitchell. Isn't he wonderful?