From Proto-Indo-European *ur, *uh₁r-; compare Ancient Greek οὖρον (oûron), ούρα (oúra, “urine”); variant of root *awer- (“to moisten, flow”), cf. *weh₁r- (“water, liquid, milk”). See also Sanskrit वार् (vār, “water”), Avestan (var, “rain”), Lithuanian jūra (“sea”), Old English wær, Old Norse ver (“sea”), ur (“drizzling rain”).

Просто "лью", ср. "роняю"

Сонце - обычное выпадение "л"

Соль, родственно серый, зола