With most historical falsehoods, it's hard to pinpoint who exactly started the whole misinterpreted mess. But this one has a clear culprit: Professor Carl Emil Doepler, the costume designer for the very first production of Richard Wagner's epic opera cycle "Der Ring de Nibelungen" in 1876 [source: The Economist]. Thousands of stagings of "The Ring" cycle worldwide have made horns the de facto Viking helmet.
So what did real Viking helmets look like? Truth is, we're not too sure. Viking remains have been dug up across Scandinavia, but archaeologists have found only one helmet, a rounded iron cap with a nose guard, but nary a horn in sight. (It doesn't seem too practical to have a helmet with horns, since they could get tangled in tree branches). Doepler may have taken his inspiration from pre-Viking cultures in Northern Europe that used helmets with horns or antlers in religious rites [source: History.com]. Or you can blame Elmer Fudd.