The 13th-century Scottish philosopher and theologian John Duns Scotus was a highly educated man. But that didn’t stop him from believing that a pointy hat could make him smarter.
What we now see as a mark of stupidity today, the dunce cap originated with the philosopher-priest and his followers, the Dunsemen.
While some say John Duns Scotus was inspired by the image of wizards, others claim it was the other way around – the dunce caps inspired people to depict wizards in pointy hats.
In any case, the idea is that the cap acts as a reverse funnel, drawing in knowledge and letting it melt down into the brain.
The highly analytical writings of the medieval scholar fell out of favor in the more humanistic Renaissance, so it is perhaps the case that his followers were seen as…well, remedial, as time went on. As the Dunsemen came to be seen as foolish, their hats became a marker of that, signifying someone who is a lot less intelligent than Scotus once was.
However, the word “dunce” as we use it today originated in a play in the 17th century, which referred to a “dunce table” where children and dull guests were made to sit. In 1840, Charles Dickens mentioned the dunce cap in The Old Curiosity Shop, in which he described it as a leftover relic in a classroom made of newspaper. However, his mention and lack of further explanation mean it was probably something people would have already known about.
After that, the dunce cap served as a warning to children that when they misbehaved in class, they would be forced to sit in the corner wearing it. – WTF fun facts
Source: “The Dunce Cap Wasn’t Always So Stupid” — Atlas Obscura