'traitorous' originates from Late Middle English, formed from 'traitor' + the adjective suffix '-ous'. 'Traitor' comes via Old French 'traitour' from Latin 'traditor', where 'tradere' meant 'to hand over' (from 'trans-' meaning 'across' + 'dare' meaning 'to give').

'traitorous' developed as an adjective based on Middle English 'traitour'/'traitor' (from Old French 'traitour'), which in turn came from Latin 'traditor'; the suffix '-ous' (from Latin '-osus') was added to form the adjective, giving modern English 'traitorous'.

Originally related to the idea of 'one who hands over' or 'a betrayer' (Latin 'traditor'), the term evolved into an adjective meaning 'showing betrayal or disloyalty' in modern English.