'bad-tempered' originates from the combination of 'bad' and 'tempered,' where 'bad' meant 'not good' and 'tempered' referred to one's disposition or mood.

'bad-tempered' evolved from the Middle English word 'tempered,' which referred to one's mood or disposition, combined with 'bad' to describe a negative mood.

Initially, it meant 'having a negative disposition,' and this meaning has largely remained the same in modern usage.