'blunder' originates from Middle English, specifically the word 'blunderen,' where 'blunderen' meant 'to stumble or make a mistake.'

'blunderen' transformed into the modern English word 'blunder,' and 'blunderer' was derived to describe someone who frequently makes such mistakes.

Initially, it meant 'to stumble or make a mistake,' but over time it evolved into its current meaning of 'a person who makes careless or stupid mistakes.'