A verb appearing in the Gnomish Lexicon of the 1910s as G. gwil- “sail, float, fly” derived from ᴱ√gu̯il (GL/45). It was cognate to ᴱQ. vil- or ’wili- “sail, fly, float” (QL/104).
Neo-Sindarin: Since [ᴹQ.] vil- or wil- “fly” survived in Tolkien’s later writings (Ety/WIL), I would retain ᴺS. gwil- as well, but only for the sense “to fly”. For “float” and “sail” I would use other verbs like ᴺS. loda- “float” [N. lhoda-] and ᴺS. renia- “sail” [N. rhenia-].
A word in the Gnomish Lexicon of the 1910s said to be used like gwilm “quiet, rest, peace”, but also meaning “cessation, quiescence, leaving off” (GL/45). It was derived from primitive ᴱ✶gu̯ild- base on the early root ᴱ√gwil-.