'light-directed' is a compound formed from the English word 'light' and the past-participial adjective 'directed' (from 'direct'). 'Light' comes from Old English 'lēoht' meaning 'brightness'; 'directed' ultimately derives from Latin 'directus' (past participle of 'dirigere') meaning 'set straight' or 'guided'.

'light' originates from Old English 'lēoht' and developed into Middle English 'light' before becoming modern 'light'. 'Direct' comes from Latin 'dirigere' > Latin past participle 'directus', passed into Old French and Middle English as 'direct', and the participial form produced adjectives like 'directed'; combining them as a compound adjective produced 'light-directed' in modern technical and descriptive usage.

Initially, 'light' referred simply to brightness or daylight and 'direct' meant to set straight or guide; combined as 'light-directed' it came to mean 'guided or oriented by light' in technical and biological contexts (e.g., describing movement or growth influenced by light).