meneg (#probably “thousand”) + groth (“large underground dwelling”)
Sindarin
menegroth
place name. Thousand Caves
Menegroth
noun. thousand caves
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
Doriathrin
menegroth
place name. Thousand Caves
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).