gîl (pl. of gîl “star, bright spark”) + thóniel (perf. act. part. of than- “kindle, set light to”) #[HKF] it is possible that iel is just iell “daughter” [Etym. SEL-D] traditional ending for women’s names.
_ theon. _Starkindler (in past). thoniel
theon.'Star-kindler'. Q. Tintalle. THĂN/THĀN << TÁN << TON; ÑGIL << GIL.
gilthonielfeminine name. Starkindler, Star-kindler, who lit the stars
A title of Elbereth (LotR/238) translated “Star-kindler” (RGEO/64, Let/278), the equivalent of Q. Tintallë (MR/388). This name is a combination of gil “star”, a derivative of the root √THAN “kindle” and the feminine suffix -iel¹ (PE17/22-3, MR/388).
Conceptual Development: The name N. Gilthoniel appeared in The Etymologies from the 1930s with essentially the same derivation as the one given above, except that the middle element was from the root ᴹ√TAN¹ “make, fashion”, and the gloss was “Star-maker” (Ety/GIL, TAN). When this name first appeared in Lord of the Rings drafts from the 1940s, it was Gilthonieth, a form that also appeared in The Etymologies, but it was soon revised to Gilthoniel (RS/68). In some notes from the 1950s, Tolkien considered the possibility that the final element thoniel was a special past-tense agental formation meaning “kindler (in the past)” (PE17/82).