'apoplexious' originates from Greek, specifically the word 'apoplēxia' (ἀποπληξία), where 'apo-' meant 'away' and 'plēssō' (via a noun form) related to 'to strike'. The adjective was formed in English by adding the suffix '-ous' to the noun 'apoplexy'.

'apoplexious' developed from Medieval/Modern Latin 'apoplexia' and the English noun 'apoplexy'; the adjective form emerged in Early Modern English (from 'apoplexy' + '-ous'), paralleling older adjectives such as 'apoplectical'.

Initially it referred specifically to being stricken by apoplexy (a medical stroke); over time it also came to be used figuratively to mean 'extremely angry' or 'apoplectic with rage'.