A noun in Late Notes on Verb Structure (LVS) written in 1969, given as hanw̃a “seat” and derived from primitive ✶khadmā where dm became nm [χanmā] and then nw (PE22/148). Early iterations of this word also meant “chair”, so this word may have that meaning as well.
Conceptual Development: The earliest “seat” words were ᴱQ. sōra {“seat, throne” >>} “seat” and ᴱQ. sonda “seat, chair” in the Qenya Lexicon of the 1910s under the early root ᴱ√SOŘO [SOÐO] (QL/85-86). Tolkien revised the root to ᴱ√SORO (ÐORO) after which the form sonda was deleted. In the contemporaneous Poetic and Mythological Words of Eldarissa Tolkien had only ᴱQ. sonda “seat” (PME/86).
In The Etymologies of the 1930s Tolkien had ᴹQ. handa “chair” under the root ᴹ√KHAD, but Tolkien revised the root to ᴹ√KHAM “sit” and the Quenya form to ᴹQ. hamma “chair” (Ety/KHAM; EtyAC/KHAM). Tolkien then introduced a new root ᴹ√KHAM “call to, summon”, saying that “KHAM sit (replacing KHAD, cancelled)”, so apparently the root for “sit” reverted back to KHAD. This is supported by the 1969 “seat” word hanwa seen above.
A word appearing as haðw “seat” in Late Notes on Verb Structure from 1969 derived from primitive ✶khadmā (PE22/148). In more typical Sindarin orthography it would be hadhu. Based on earlier versions of this word, it may mean “✱chair” as well (see below).
Conceptual Development: The Gnomish Lexicon of the 1910s had G. dorn “seat” (GL/19), clearly based on the early root ᴱ√ÐORO “sit” (QL/85). In Early Noldorin Word-lists this became ᴱN. {hód >>} haud “seat” (PE13/147).
A draft entry to The Etymologies of the 1930s had N. hand “seat” and N. hanw “chair” derived from the root ᴹ√KHAD (EtyAC/KHAM). Tolkien updated this root form to ᴹ√KHAM “sit” with a noun form N. ham or hanw, with a hard-to-read gloss that was probably “?chair” (Ety/KHAM; EtyAC/KHAM). Tolkien then created yet another root ᴹ√KHAM “call to, summon”, saying that “KHAM sit (replacing KHAD, cancelled)”, so apparently the root for “sit” reverted back to KHAD. This is supported by the 1969 “seat” word haðw seen above.