A word for “sky” in an early name list from the 1910s and appearing in a couple early names: G. Thlim Quing Ilon “✱Folk of the Heavenly Arc” and G. Cris o Teld Quing Ilon “Gully of the Rainbow Roof” (PE13/101, 104), the latter revised to G. Cris Ilbranteloth (LT2/202). In the contemporaneous Gnomish Lexicon, however, G. Ilon was the name of Ilúvatar (GL/50).
Gnomish
hel-
verb. to freeze
dai
noun. sky
ilon
noun. sky
luithon
noun. sky
A word for “sky” in the Gnomish Lexicon of the 1910s, an elaboration of G. lui “blueness” (GL/55).
The verb G. hel- “freeze” appeared in the Gnomish Lexicon of the 1910s as derivative of primitive χele-k (GL/48), based on the early root ᴱ√HELE as suggested by Christopher Tolkien (LT1A/Helkar; QL/39).
Neo-Sindarin: Since √KHEL appeared in later writings with glosses like “freeze” (Ety/KHEL) and “ice” (PE17/116), I think ᴺS. hel- “to freeze” can salvaged for Neo-Sindarin.