Silmarilradiance of pure light
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".
name. 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 rillë “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 probably a compound of ᴱQ. Sil “Moon” and ᴱQ. marilla “pearl” (LT1A/Silmaril). 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.