That reminds me of that monk joke......

A new monk joins an abbey and dedicates his life to copying ancient books by hand.

After the first day though, he reports to the head priest. He's concerned that all the monks have been copying copies made from still more copies.

"If someone made a mistake," he points out. "It would be impossible to detect. Even worse, the error would continue to be made."

A bit startled, the priest decides he better check their latest effort against the original which is kept in a vault beneath the abbey. A place only he has access to.

Well two days, then three days pass without the priest resurfacing. Finally, the new monk decides to see if the guy is alright. When he gets down there though, he discovers the priest hunched over both a copy and the original text. He is sobbing and by the looks of it has been sobbing for quite some time.

"Father?" the monk whispers.

"Oh my goodness," the priest wails. "The word is 'celebrate.' "

It's from Latin in- (meaning "in" or "on") and dorsum (meaning "back"). Indorse comes to English through medieval Latin, and changed forms in the 15th century to endorse, around the time the roots of our modern court system took roots in Florence during the Inquisition.

The Florentine republic relied heavily on maritime trade, and so the court system was generally modeled around adjudication of Maritime law. Using the older Latin form lets creditors and courts know that the Sovereign is asserting Commerce law, the Law of the Land.

Am I making this up? Maybe.