Note: Outside of Anglo-French, arsun, arson (with a by-form arsion) is sparsely attested in Old and Middle French. Französisches etymologisches Wörterbuch notes that medieval attestations and later survivals are markedly regional (west and southwest France, including Normandy and Francophone Brittany). — The normal suffix of verbal action in later classical Latin and Late Latin was -tiōn-, -tiō, added to the verbal base (competing with the u-stem suffix -tus more common in earlier Latin), with the exception of a small number of formations with -iōn-, -iō (see condition entry 1, legion entry 1, region). Because the phonetic stem changes conditioned by the verbal adjective/past participle suffix -tus (Indo-European *-tos) are identical to those conditioned by -tiōn-, -tiō, new formations with this suffix in post-classical Latin and proto-Romance copy the morphophonemic alterations of the verbal adjective. This is evident in *ārsiō, formed from ārdēre. Note that the perfect ārsī and presumed (?) supine ārsum are most likely themselves analogical forms based on second-conjugation verbs such as mansī, mansum (from manēre "to wait, remain"), given that ārdēre (from āridus, ārdus "dry") cannot be of great antiquity in Latin.