The cave-palace of Thingol in Doriath, translated “Thousand Caves” (S/56). It is a combination of meneg “thousand” and groth “cave” (SA/groth, WJ/415).
Conceptual Development: The name Ilk. Menegroth appeared in Silmarillion drafts from the 1930s (LR/114, LR/220), and was designated as Doriathrin [Ilkorin] in The Etymologies, where it had essentially the same derivation as given above (Ety/ROD). In one late note the name was given as Menegrond, which might be a “pure Sindarin” form of this name as suggested by Carl Hostetter (NM/365).
A word for a “thousand” implied by the name Menegroth “Thousand Caves” (S/56; WJ/415). It is possible this word simply means “✱a large number” rather than being precisely 1000.
Conceptual Development: In the 1930s, the name Menegroth was Ilkorin (Ety/ROD), and thus the word meneg likely also belonged to that language. The Gnomish Lexicon of the 1910s had G. moth(in) or mothwen “thousand”, originally meaning “flock” and related to G. moth “sheep” (GL/58).