A noun appearing as G. gwelc “bubble” in the Gnomish Lexicon of the 1910s (GL/44). It is clearly based on the early root {ᴱ√WELE >>} ᴱ√GWELE from the contemporaneous Qenya Lexicon (QL/103).

Neo-Sindarin: Since we have no better “bubble” words, I would adapt this as ᴺS. gwelch “bubble” for purposes of Neo-Sindarin, but assume it is derived from a Neo-Root ᴺ√WEL so that it retains the initial w, and with the usual sound Sindarin change of ancient lk to lch.