'aroar' originates from Middle English, specifically formed from the prefix 'a-' plus the verb 'roar', where the prefix 'a-' meant 'in' or 'on' and 'roar' meant 'to make a loud deep sound'.

'aroar' appeared in Middle English in forms such as 'a-rore' / 'aroore' and eventually became the modern English word 'aroar'.

Initially, it meant 'in a state of roaring (making a loud noise)', but over time it evolved into its current sense of 'in a state of noisy excitement or uproar'.