Etymology: < Anglo-Norman arsun, arçoun, Anglo-Norman and Middle French arson saddle-bow (c1100 in Old French as arçun ), (in plural) saddle (late 12th cent.) < post-classical Latin arcion- , arcio (late 11th cent.) < classical Latin arcus bow (see arc n.) + -iō -ion suffix¹. Compare archon n.¹Compare post-classical Latin arcionus, arco, arso, arzo (13th cent. in British sources; from 14th cent. in continental sources; < Old French), and also Old Occitan arço, arso, etc. (c1200), Catalan arçó (13th cent.), Spanish arzón (a1207), Portuguese arção (13th cent.), Italian arcione (13th cent.). It is unclear whether the following earlier quot. should be taken as showing the Anglo-Norman or the Middle English word in a Latin context:1278 in J. T. Fowler Extracts Acct. Rolls Abbey of Durham (1899) II. 487 In 2 paribus de arsuns. Earlier currency of the English noun is apparently not implied by the surname Arnulf le Arcuner (?a1216), Arnold Arcener (in an undated source from Middlesex), which probably reflects Old French arçoneres, arcenour, etc., Middle French arçonneur, arçounneur, etc. (13th cent.), of uncertain and disputed meaning (probably ‘worker who removes impurities from wool or silk by hitting it with an instrument called arçon’ rather than ‘maker of saddle-bows’); for a discussion of the meaning of the French agent noun see Französisches etymol. Wörterbuch XXV. at *arcio.

Etymology: < Anglo-Norman and Law French arson (in Anglo-Norman also as arsoun , arsun , etc.; compare Old French arsun , Old French, Middle French arson , arsion ) crime of intentionally or recklessly destroying or damaging property by setting fire to it (second half of the 12th cent.; first half of the 12th cent. in sense ‘action of burning a person alive’) < post-classical Latin arsion- , arsio (from 13th cent. in British sources in this sense (also as arcio ); 14th cent. in a continental source; 1086 in a British source denoting assaying of silver) < classical Latin ars- , past participial stem of ardēre to burn (see ardent adj.) + -iō -ion suffix¹.Compare post-classical Latin arso, arsona (13th cent. in British sources), arsina, arsinum (11th cent.; 13th cent. in a British source).