Knitwear stall, Bergen.
No, Vikings didn't have horns on their hats, but the hats are still funny.
"Forget almost every Viking costume you’ve ever seen. Yes, the pugnacious Scandinavians probably sported headgear when they marched into battle, but there’s no reason to believe it was festooned with horns. In depictions dating from the Viking age—between the eighth and 11th centuries—warriors appear either bareheaded or clad in simple helmets likely made of either iron or leather. And despite years of searching, archaeologists have yet to uncover a Viking-era helmet embellished with horns. In fact, only one complete helmet that can definitively be called “Viking” has turned up. Discovered in 1943 on Gjermundbu farm in Norway, the 10th-century artifact has a rounded iron cap, a guard around the eyes and nose, and no horns to speak of.
The popular image of the strapping Viking in a horned helmet dates back to the 1800s, when Scandinavian artists like Sweden’s Gustav Malmström included the headgear in their portrayals of the raiders. When Wagner staged his “Der Ring des Nibelungen” opera cycle in the 1870s, costume designer Carl Emil Doepler created horned helmets for the Viking characters, and an enduring stereotype was born.
Malmström, Doepler and others may have been inspired by 19th-century discoveries of ancient horned helmets that later turned out to predate the Vikings. They may also have taken a cue from ancient Greek and Roman chroniclers, who described northern Europeans wearing helmets adorned with all manner of ornaments, including horns, wings and antlers. But not only did this headgear fall out of fashion at least a century before the Vikings appeared, it was likely only donned for ceremonial purposes by Norse and Germanic priests. After all, horns’ practicality in actual combat is dubious at best. Sure, they could help intimidate enemies and maybe even poke out a few eyes, but they would have been even more likely to get entangled in a tree branch or embedded in a shield. " (From History.com)