√SIL root. “shine (white or silver)”
Tolkien used the root √SIL and its variant √THIL for Elvish words for shining things for most of his life. This root first appeared in the Qenya Lexicon as unglossed ᴱ√SILI with variant ᴱ√ÞILI and derivatives like ᴱQ. Sil “Moon”, ᴱQ. sili- “gleam, glint”, ᴱQ. silik “flint”, and ᴱQ. silqe “glossy hair” (QL/83), though last of these was the result of blending with ᴱ√SḶKḶ² “rich, lush”, variant of ᴱ√SṚKṚ “fat” (QL/86). The contemporaneous Gnomish Lexicon had derivatives like G. Sil “Moon” and G. silc “flint” pointing only to ᴱ√SILI (GL/67); the only indication of variant ᴱ√ÞILI was in unglossed G. thil followed by deleted forms like G. Thil “Moon” (GL/72).
By The Etymologies of the 1930s, the variants ᴹ√SIL “shine silver” and ᴹ√THIL were better established (Ety/SIL, THIL). The variant ᴹ√SIL had derivatives like ᴹQ. silme/N. silif “moonlight, light of Silpion” and the extend form ᴹ√SÍLIP from which ᴹQ. Silpion was derived (Ety/SIL), and its most notable use from the 1930s forward was as the basis for the initial element of Q. Silmaril vs. S./N. silef as in N. Silevril (Ety/SIL; PE17/23; Let/425). The variant ᴹ√THIL had derivatives like ᴹQ. Isil/N. Ithil “Moon, (lit.) the Sheen” (Ety/THIL), forms Tolkien also retained from the 1930s forward. Tolkien mentioned both root variants √SIL and √THIL with the glosses like “shine (white or silver)” regularly in his later writings (Let/425; PE17/66; PE22/136; SA/sil).
References ✧ Let/425; PE22/136; SA/sil
ᴹ√SIL root. “shine silver”
References ✧ Ety/RIL, SIL, THIL
ᴱ√SILI root. “*gleam”
References ✧ LT1A/Sil; QL/83, 86, 92