ᴹ√ƷEL root. “sky”
A root in The Etymologies of the 1930s glossed “sky”, with derivatives like ᴹQ. helle/N. ell “sky” and ᴹQ. helwa/N. elw “(pale) blue” (Ety/ƷEL). It was the basis for the initial elements of the names N. Elrond, N. Elwing and ᴹQ. Elwe, but elsewhere Tolkien connected these names to √EL “star”. It was also an element in the word N. eilian(w) “rainbow, (lit.) sky-bridge”, later given as S. ninniach. On the basis of these changes, I think it is likely Tolkien abandoned ᴹ√ƷEL, but some of its derived words are still popular in Neo-Eldarin.
References ✧ Ety/ƷEL, YAT