'daft' originates from Old English, specifically the word 'gedæfte', where the prefix 'ge-' was a common verbal/adjectival prefix and 'dæfte' meant 'mild' or 'tame'.

'daft' changed from Old English 'gedæfte' into Middle English forms such as 'daft' or 'dafte', and through regional (especially northern) dialectal shifts the meaning shifted and the modern English form 'daft' emerged.

Initially, it meant 'mild' or 'tame', but over time (especially from late Middle English into modern English) it developed the sense of 'silly' or 'foolish' and later also 'mentally unsound'.