'non-photropic' originates from modern English, formed by prefixing 'non-' and the adjective 'photropic'/'phototropic'. 'non-' comes from Latin 'non' meaning 'not', while 'photo-' traces to Greek 'phōs' meaning 'light' and '-tropic' to Greek 'tropos' meaning 'turn'.

'phototropic' entered English via New Latin from Greek 'phototropikos' ('photo-' + 'tropos'), meaning 'turning toward light'. The compound 'non-phototropic' is a modern negated formation using the productive English prefix 'non-'.

Initially, 'phototropic' meant 'turning toward (or away from) light'; 'non-phototropic' has simply negated that sense and means 'not showing phototropism' with little semantic shift since its coinage.