'petulant' originates from Latin, specifically the word 'petulans', where 'petere' meant 'to seek, to attack' and the suffix '-ant' indicated an agent or characteristic.

'petulans' passed into Medieval Latin and French and then into English as 'petulant' by way of Late Middle English, eventually giving the adverbial form 'petulantly'.

Initially it meant 'impetuous, insolent' in Latin, but over time it evolved to mean 'childishly sulky or impatiently irritable' in modern English.