'blunder' originates from Scandinavian languages, specifically Old Norse 'blundra', where 'blund-' meant 'to doze or shut the eyes'.

'blunder' changed from Middle English forms such as 'blundren'/'blunderen' (influenced by Scandinavian verbs) and eventually became the modern English verb 'blunder' and the agent noun 'blunderer'.

Initially, it meant 'to doze or be half-asleep', but over time it evolved into its current meaning of 'to make a stupid or careless mistake'.