'besmirch' originates from Middle English, specifically the word 'besmirchen,' where 'be-' meant 'thoroughly' and 'smirch' meant 'to soil or stain.'

'besmirchen' transformed into the modern English word 'besmirch.'

Initially, it meant 'to soil or stain thoroughly,' but over time it evolved into its current meaning of 'to damage the reputation of someone or something.'