The most common Sindarin word for “hollow” as mentioned in the Quendi and Eldar essay from 1959-60, derived from primitive ✶kuldā (WJ/414).
Conceptual Development: The Gnomish Lexicon of the 1910s had G. cub “hollow” with deleted variant {cûf >>} (GL/27), probably based on the early root ᴱ√KUPU “hump” (QL/49).
A word for “cloak, mantle” implied by the name Thingol “Grey Cloak, Grey Mantle” and its Quenya cognate Sindacollo containing Q. collo “cloak” (S/56; SA/thin(d); PE17/72), clearly derived from √KOL “bear, carry, wear” (PE17/158).
Conceptual Development: The Gnomish Lexicon of the 1910s had G. tôl “a mantle” related to G. tô “wool” (GL/71).