'ill-omened' originates from English, specifically the compound of the adjective 'ill' and the noun 'omen', where 'ill' (from Old English 'yfel') meant 'bad' and 'omen' (from Latin 'omen') meant 'sign'.

'ill-omened' appeared in Middle English as forms like 'illomened' (a compound of 'ill' + 'omen' with the adjectival suffix '-ed') and eventually became the modern hyphenated form 'ill-omened'. The element 'omen' itself comes from Latin 'omen'.

Initially, it meant 'having a bad omen' in a literal sense, but over time the usage broadened to include the more general senses of 'ominous' and 'unlucky'.