illuminate: [16] Etymologically, illuminate is a parallel construction to enlighten. It was formed in the late Latin period from the prefix in- and lūmen ‘light’ (source of English luminous). The past participle of the resulting illumināre gave English illuminate. The medieval-sounding sense ‘illustrate manuscripts’ is actually quite recent, replacing in the 18th century the parallel formation enlumine, acquired by English in the 14th century via Old French enluminer from medieval Latin inlūmināre. Illumine [14] came via Old French illuminer. Illustrate is closely related. => illustrate, luminous[illuminate etymology, illuminate origin, 英语词源]