A root in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. wele-/G. gwel- “to boil, bubble” and ᴱQ. welbe/G. gwelc “bubble” (QL/103; GL/44). There are no signs of this root in Tolkien’s later writing, but I think it is worth retaining for the purposes of Neo-Eldarin, since there are no other good candidates for “boil” words elsewhere in the published corpus. To retain the Gnomish derivatives of this root, I would assume the strengthening of w- to gw- was later, after the Ancient Telerin sound change of gw > b.
References ✧ QL/103