'photropic' originates from Greek, specifically the elements 'phōs/phot-' and 'tropos', where 'phōs' meant 'light' and 'tropos' meant 'turn'.

'photropic' developed via New Latin/Modern Latin formation from Greek 'phototropikos' (from 'phōs' + 'tropos') into Late Latin/Neo-Latin 'photropicus/phototropicus' and eventually entered English as 'phototropic'.

Initially it meant 'turning toward light' in a literal, biological sense, and this core meaning has been retained in modern usage to describe organisms or parts that move or grow toward light.