A Primitive Adûnaic word glossed “crow” (SD/426). Tolkien gave two primitive forms of this word, khāw and khăw, which could just be variant forms of the same root ✱KHAW. A more intriguing possibility is that khāw is actually the subjective form of khăw, since this would indicate that this subjective formation dates back to the primitive stages of the language. As evidence of this, the derived plural khāwī(m) (SD/426) does resemble the Classical Adûnaic subjective plural.
Contradicting this conjecture is the fact that khaw, as an animal name, should be declined as a common-noun, using the common subjective suffix -an. Elsewhere, though, Tolkien declined some animal names as if they were neuter nouns, for example narîka as the subjective plural of #narak (SD/251). Perhaps not all animals were common nouns, or perhaps Tolkien’s ideas for the subjective tense were not fully formed when these examples were written.
The early existence of this root was indicated in the Gnomish Lexicon of the 1910s as (unglossed) ᴱ✶haw- where it was the basis of words like G. hau- “to lie” and G. haus “bed” (GL/48). It reappeared in The Etymologies of the 1930s as ᴹ√KHAW “rest, lie at ease”, this time with both Quenya and Noldorin derivatives such as ᴹQ. hauta- “cease, take a rest, stop” and N. haust “bed” (Ety/KHAW). In The Etymologies Tolkien also said this root influenced the meaning of N. hauð “mound” so that it came to mean “grave, tomb” as well (Ety/KHAG, KHAW).
The root reappeared again in revisions made to the Outline of Phonology (OP2) around 1959 with a new gloss “cover up, hide away, lay in store”, along with an extended root √KHAWAD “store, hoard” that continued to influence S. haudh “(funeral) mound” (PE19/91). The root √KHAW >> √KHAWA also appeared in a page of roots having to do with “large and small” probably from around 1968 (VT47/26 note #26), with the derivatives Q. höa “big, large” and Q. haura “huge” (PE17/115).
Neo-Eldarin: For purposes of Neo-Eldarin, I think the 1930s meaning “rest, lie at ease” is probably most useful, and I would limit the meaning “lay in store” to its extended root √KHAWAD. As for the meaning “big”, I would limit it to (Quenya-only) Q. höa.