'sneaky' originates from the word 'sneak,' which comes from Middle English 'sneken,' meaning 'to creep or move stealthily.'

'sneken' transformed into the modern English word 'sneak,' and 'sneaky' was derived from it to describe the characteristic of being stealthy.

Initially, it meant 'to move stealthily,' but over time it evolved into describing a characteristic of being secretive or stealthy.