'oxidise' ultimately derives from the noun 'oxide' + the verb-forming suffix '-ise'; 'oxide' entered English from French 'oxyde' and Modern Latin 'oxydum',

'oxide' came into English via French 'oxyde' from Modern Latin 'oxydum', which ultimately traces to Greek 'oxys' meaning 'sharp' or 'acid'; the verb was formed in English in the 19th century as 'oxidize' (US) / 'oxidise' (UK) from 'oxide' + '-ize'/'-ise'.

Initially it referred specifically to forming an oxide (combining with oxygen); over time it broadened to mean any process of oxidation (including electron loss in redox chemistry) and the modern sense remains closely related.