Gnomish
hîl
noun. frost
helc
adjective. ice-cold, icy, cold
hel-
verb. to freeze
heloth
noun. frost
helw
adjective. ice-cold, icy, cold
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
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.