illustrious (adj.)youdaoicibaDictYouDict[illustrious 词源字典]
1560s, from Latin illustris "lighted, bright, brilliant;" figuratively "distinguished, famous," probably a back-formation from illustrare "embellish, distinguish, make famous" (see illustration). Sometimes also illustrous. Replaced illustre in same sense (mid-15c.), from Middle French illustre.[illustrious etymology, illustrious origin, 英语词源]