Berserk was first used in English in the early 19th century, in reference to ancient Norse warriors, berserkers, who fought with furious violence. The word derives from Old Norse berserkr, probably from bjorn ‘bear’ + serkr ‘coat’; it has been suggested that warriors performed a war dance wearing bearskins to imbue them with the bear's strength before battle. The word has also been explained as being from berr ‘bare’ (i.e. without armour).