'straight-eyed' originates from Modern English, specifically a compound of the adjective 'straight' and the adjective-derived element 'eyed' (from 'eye'), where 'straight' meant 'not bent; direct' and 'eye' referred to 'the organ of sight.'

'straight' comes from Old English 'streht'/'straeht' (from Proto-Germanic *strakaz) meaning 'straight, stiff'; 'eye' comes from Old English 'eage' (from Proto-Germanic *auga-). These elements combined in English to form compound adjectives such as 'straight-eyed' in later stages of English (Early Modern to Modern English).

Initially the components referred simply to 'straight' + 'eye/eyed' (a literal description of eye direction), but over time the compound has been used figuratively to mean a steady, direct, or unflinching gaze.