The mansion of Manwë and Varda on Taniquetil, translated as “mansion of the high airs” (LotR/235, RC/217). The etymology of this name is unclear, but it is probably derived from Ilma “Starlight”, and related to Ilmen “Place of (Star)light” (SA/ilm).
Conceptual Development: The name ᴹQ. Ilmarin first appeared in Lord of the Rings drafts from the 1940s (TI/92). It did not appear in The Silmarillion proper, though it was discussed by Christopher Tolkien in The Silmarillion index and appendix (SI/Taniquetil, SA/ilm).
Ilmarin noun "mansion of the high airs", the dwelling of Manwë and Varda upon Oiolossë (SA:ilm-)