arson:  Like ardour and ardent, arson comes from the Latin verb ardēre ‘burn’. Its past participle was arsus, from which was formed the noun arsiō ‘act of burning’. This passed via Old French into Anglo-Norman as arson, and in fact was in use in the Anglo-Norman legal language of England from the 13th century onwards (it occurs in the Statute of Westminster 1275). The jurist Sir Matthew Hale was the first to use the word in a vernacular text, in 1680. Other words in English ultimately related to it include arid and probably ash, area, and azalea. => ardour, area, ash, azalea
1670s, from Anglo-French arsoun (late 13c.), Old French arsion, from Late Latin arsionem (nominative arsio) "a burning," noun of action from past participle stem of Latin ardere "to burn," from PIE root *as- "to burn, glow" (see ash (n.1)). The Old English term was bærnet, literally "burning;" and Coke has indictment of burning (1640).