When most of us think of Vikings we think of fearsome warriors wearing horned helmets…or perhaps of their caricature in Hagar the Horrible comic strips. But did you know that Vikings never wore horns on their helmets? They would have snagged on weapons. But the Scandinavian Viking raiders and traders who swept through Europe so effectively from the 8th to the 11th centuries AD were pagans, so leaders of the Christian church at the time had to demonise them. Hence they depicted them at every opportunity with horns.
Source: reported in Talkback Trash and Treasure