Silmaril (Silmarill-, as in pl. Silmarilli), noun, name of the shining jewels made by Fëanor; full sg. form Silmarillë (SA:sil, SIL, RIL, MIR).Translated "radiance of pure light" in Letters:148. Gen. pl. Silmarillion, as in (Quenta) Silmarillion "(the Story) of the Silmarils".
Quenya
silmaril
proper name. Great Jewel
Silmaril
radiance of pure light
The name of the great jewels crafted by Fëanor from which The Silmarillion legends gets their name (S/33). It sometimes appeared in the longer form Silmarillë (PE17/47, PM/363). Tolkien translated this name as “radiance of pure light” (Let/148) and said that it was a combination of silima, the crystaline substance from which the jewels were made (RGEO/65), and a derivative of the root √RIL “brilliant, brilliance” (PM/363), perhaps in the form [ᴹQ.] rille “brilliance”.
Conceptual Development: The name ᴱQ. Silmaril dates back to the earliest Lost Tales (LT1/128). Christopher Tolkien suggested that at this early stage it was a compound of ᴱQ. Sil “Moon” and ᴱQ. marilla “pearl” (LT1A/Silmaril), which is consistent with its Gnomish cognate G. Silubrilt. In The Etymologies, the name ᴹQ. Silmaril appears as a combination of silma “silver, shining white” and the root ᴹ√RIL (Ety/RIL, SIL), similar to its later etymology.