The most general Quenya word for “house” or small building derived from √KAW “shelter” (PE17/107; VT47/35; WJ/369). As Tolkien described it in notes from the late 1960s:
> From √KAW was made the simple primitive form ✱kawā > Q koa, applied to any “shelter” (contrived and not natural) temporary or in Aman more often permanent, and applied to what we might call outhouses, huts, sheds, booths (PE17/108).
In another note from this period:
> As the simple name of a building used for a dwelling or other purposes Quenya used koa, a derivative of √KAW “shelter” (PE17/165).
Thus coa could be used for a “house” as a dwelling place but also for other kinds of small buildings as well. For an inhabited dwelling, Q. mar(da) might be more appropriate.
In some places Tolkien use coa to refer (metaphorically) to a body, as in cöacalina “light of the house” referring to a spirit within a body (MR/250), as well as the phrase: Valar ar Maiar fantaner nassentar fanainen ve quenderinwe koar al larmar “Valar and Maiar cloaked their true-being in fanar [veils], like to Elvish bodies [koar = houses] and raiment” (PE17/175).
coa ("köa")noun "house" (VT47:35, with etymology); coarya "his house" (WJ:369), allative coaryanna ("k") "to/at his house" (VT49:23, 35), quenderinwë coar ("koar") "Elvish bodies" (PE17:175). Notice how coa "house" is here used metaphorically = "body", as also in the compound coacalina "light of the house"(a metaphor for the soul [fëa] dwelling inside the body [hroa]) (MR:250)