The name Lleu is derived from Proto-Celtic *Lugus, the exact meaning (and etymology) of which is still a matter of scholarly debate [REF].
Proto-Celtic *Lugus may be related to the root of the Proto-Celtic *lug-rā 'moon' (the origin of Welsh lloer, though Peter Schrijver suggests an alternative etymology for lloer, from Common Celtic *lus-rā, where the root would be cognate with that of Latin luridus [earlier *lus-idus] "pale yellow").