The future King and Queen took part in a recent visit to Scotland earlier in the week, as part of their Royal duties. It was there that fans were a little confused about why they were called the Duke and Duchess of Rothesay as they walked around Stirling and Falkirk.

Still, there’s actually a rather simple explanation for it.

It’s a 700-year-old tradition that royal author Robert Jobson wrote about in 2022, per the William at 40: The Making of a Modern Monarch.

“North of the England border they’re known as the Duke and Duchess of Rothesay,” he shared on the Mail’s Palace Confidential podcast.

“It’s a title which dates back to when Scotland was an entirely separate kingdom before the union with England,” he added.

“The title descends from that given to. I think one of the first kings of Scotland gave to his eldest son and its descended ever since the early 14th Century.”

To be precise, it dates back to 1396, per Royal Central, and was known to be a title passed down to the heir apparent of the Scottish Crown.