Comparative evidence

leu̯k

• Hitt. lukk- 'get light', 'light up', 'dawn', 'grow bright' (CHD L-N: 74ff., EDHIL: 530ff.)

• Hitt. lukki- 'set fire' (to) (CHD L-N: 78f.)

• Hitt. lalukess- 'become bright', 'shine', 'glow', 'glisten" (CHD L-N: 29f.)

References

EDHIL = Kloekhorst, A. 2008. Etymological Dictionary of the Hittite Inherited Lexicon. Brill.
CHD = Guterbock H.G., H.A. Hoffner, Th.P.J. van den Hout (eds.), 1980 - . The Hittite Dictionary of the Oriental Institute of the University of Chicago. Chicago.