A term for the “true firmament” where the stars dwelled. It is a compound of tar- “high” and menel “heaven” (properly, “the heavens”).
Conceptual Development: The name ᴹQ. Tarmenel first appeared in Lord of the Rings drafts from the 1940s within Bilbo’s poem at Rivendell (TI/97). This name was retained in the published version of this poem (LotR/235) making it canonical, but its exact cosmological significance is unclear. In Tolkien’s “Unfinished Index” of The Lord of the Rings, he described Tarmenel as the “Region of the Wind” (RC/216).
In one version of Tolkien’s cosmology from the mid-50s, the Tarmenel was distinct from the Nur-menel “✱Under Heaven” (“lesser firmament”) that Varda created as a barrier over Valinor against the depredations of Melkor (MR/388). The idea of a lower heaven (and the terms Tarmenel and Nurmenel) did not survive into the published version of The Silmarillion, but that book did describe the Ilmen, region of the stars through which the Sun and Moon travelled (S/99), which seems conceptually similar to Tarmenel.
In the incomplete Alcar mi Tarmenel na Erun prayer from the 1960s (translating the first two lines of Gloria in Excelsis Deo into Quenya), Tolkien used the term Tarmenel to refer to the Christian Heaven, though elsewhere he used the name Eruman for “Heaven”.
Tarmenel place-name "High Heaven" (LotR1:II ch. 1, VT44:34, in the latter source also locative tarmeneldë), Tar-menel "the true firmament", as opposed to Nur-menel (q.v.) (MR:388)