From ljūþ ‘light’ (doublet of ljuguþ, via Middle Valthungian from Old Valthungian ljuhþ, ljuhaþ, from Griutungi liuhaþ; cf. Gothic liuhaþ; uncertain relationship to ProtoGermanic leuhtą), and tungla ‘planet, orb, sphere’ (via Middle and Old Valthungian and Griutungi tungl, cf. Gothic tuggl, from ProtoGermanic tunglą). We might expect -hwerb here (‘sphere, orb’ in the geometrical sense) instead of -tungla (which usually refers to stellar phenomena – “the heavenly spheres,” if you will), but this refers more to their ability to emit light than to their shape.
(Valthungian) IPA: /ˈljuːðɑˌtuŋɡlɑ/