'sulky' originates from the English word 'sulk,' which is derived from the Old English word 'solcen,' meaning 'idle' or 'slow.'

'solcen' transformed into the Middle English word 'sulken,' and eventually became the modern English word 'sulk.'

Initially, it meant 'idle or slow,' but over time it evolved into its current meaning of 'bad-tempered or resentful.'