This invertible root and ones like it were the basis for “away” words for much of Tolkien’s life. The earliest iteration was ᴱ√AVA “go away, depart, leave” in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. au “away from” and ᴱQ. avanwa “going, passing, nearly gone” (QL/33). This early root remanifested as ᴹ√AB “go away, depart, leave” in The Etymologies of the 1930s, but the gloss of that root was revised to “refuse, deny” (Ety/AB). As a replacement, Tolkien introduced ᴹ√AWA “away, forth; out” with derivatives like ᴹQ. ava “outside”; Tolkien also considered deriving a privative prefix ᴹQ. ava- from this root (Ety/AWA).
The root √AWA was mentioned many times in Tolkien’s later writings, along with its inverted variant √WĀ, usually with the sense “away (from)” or a verbal sense “go (away), depart, pass away”. Its most detailed description appeared in the Quendi and Eldar essay of 1959-60, where Tolkien said:
> The element ✱AWA ... referred to movement away, viewed from the point of view of the thing, person, or place left. As a prefix it had probably already developed in CE the form ✱au-. The form ✱awa was originally an independent adverbial form, but appears to have been also used as a prefix (as an intensive form of ✱awa-, ✱au-). The form ✱wā- was probably originally used as a verbal stem, and possibly also in composition with verbal stems (WJ/361).
In this same document Tolkien said of Sindarin that:
> The only normal derivative [of √AWA] is the preposition o, the usual word for “from, of”. None of the forms of the element ✱awa are found as a prefix in S, probably because they became like or the same as the products of ✱wō, ✱wo (WJ/366).
Indeed, most of the attested derivatives of this root are in Quenya, but there are a couple in Sindarin, such as the aforementioned S. o from AWA, as well S. gwanwen “departed” (WJ/378) and the verb S. gwae- “go”, probably only in the limited sense “depart” (PE17/148), both from WĀ.
In late notes from 1969 Tolkien gave the root √AWA the sense “before or ago (of time)” (PE22/167 note #117; PE22/168), but I suspect this was a transient idea.
A root appearing in some late notes on verbs from around 1969, with the sense “possess, own, keep” (PE22/151). It seems to be a restoration of a much earlier root from the 1910s, which appeared as ᴱ√AW̯A in the Qenya Lexicon with derivatives having to do with wealth, such as ᴱQ. ausie “wealth” and ᴱQ. aute “rich” (QL/33), as well as Gnomish and Early Noldorin cognates G. avos “wealth” (GL/20) and ᴱN. awes “rich” (PE13/137). This root is a good example of how certain linguistic ideas could lay dormant for many years in Tolkien’s writing, only to reemerge much later. This makes it difficult to say for certain whether Tolkien really abandoned a particular idea.