An Etymological Dictionary of the German Language/Annotated/Licht
Licht, neuter, ‘light, luminary, candle,’ from Middle High German licht, Old High German lioht, neuter, ‘light, lustre, brightness’; corresponding to Old Saxon lioht, Dutch licht, Anglo-Saxon leóht, neuter, English light. The dental of the word is a suffix, as is shown by Gothic liuh-aþ (genitive -adis), neuter, ‘light, sheen.’ Old Icelandic ljós, neuter, ‘light,’ formed with a different suffix would be in Gothic *liuhs (genitive -sis); they are based on Aryan leukot-, leukt-, and leukos-, leuks-, as a double stem; compare Sanscrit rocis, neuter, Zend raocaṇh (for *rocâs, ‘lustre, light.’ The Aryan root luk, by gradation leuk, has numerous derivatives, Sanscrit ruc (rôcâmi), ‘to give light,’ rukmá-s, adjective, ‘glittering,’ substantive ‘jewels,’ rôká-s, masculine, rôcaná, neuter, ‘light’; Greek λευκός, adjective ‘white,’ ἀμφιλύκη, ‘morning twilight’; Latin lucerna, lûceo, lux, lucidus, lûna, lûmen, diluculum; Old Irish lóche (t), ‘lightning,’ lón, ‘lustre’; Old Slovenian luča, ‘ray,’ luna, feminine, ‘moon.’ In Teutonic there are also other derivatives of the Aryan root luk; compare Leuchte, licht, adjective, Lohe and Luchs, as well as Gothic lauhmuni, feminine, ‘lightning,’ lauhatjan, ‘to give light’; Old Icelandic ljóme, Anglo-Saxon leóma, Old Saxon liomo, masculine ‘lustre’; Anglo-Saxon lêgetu, Middle English leit, ‘lightning,’ and Old High German lôhazzen, ‘to lighten’; compare also Luchs. With Sanscrit rukšá, Zend raokšna, adjective, ‘bright,’ Prussian lauksnos, feminine, plural, ‘stars,’ and Old Icelandic ljós, ‘light,’ are also connected Old High German liehsen, adjective, ‘bright,’ and Anglo-Saxon lîxan, ‘to give light.’