A noun in The Etymologies of the 1930s appearing as car or carð with the gloss “house” under the root ᴹ√KAR “make, build, construct” (Ety/KAR). Its Quenya cognate ᴹQ. kar (kard-) was glossed “building, house”.
Neo-Sindarin: Given the meaning of its root, I would use cardh for any kind of building-like construction or structure for purposes of Neo-Sindarin. For an ordinary “house” where people live, I would use S. bâr.
Earliest name of Dagor-nuin-Giliath (SM/268, LR/117), with os for “under” instead of later nu(in). In The Etymologies, N. os- was given as a prefix meaning “about”.