'smelly' originates from the English word 'smell,' which comes from the Old English word 'smellan,' meaning 'to perceive an odor.'

'smellan' transformed into the Middle English word 'smellen,' and eventually became the modern English word 'smell,' from which 'smelly' is derived.

Initially, it meant 'to perceive an odor,' but over time it evolved into its current meaning of 'having a strong or unpleasant odor.'