'bob-tailed' originates from the English word 'bob,' meaning 'to cut short,' and 'tail,' referring to the rear appendage of an animal.

'bob' changed from the Middle English word 'bobben,' meaning 'to strike or cut short,' and eventually became the modern English word 'bob' in 'bob-tailed.'

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