An adjective whose basic sense is “gone, lost”, with numerous other similar translations such as “no longer to be had, vanished, departed, dead, past, over, gone for good”. The word vanwa is a good example of what I call an “anchor word”: a word that Tolkien established early in his development of Elvish and retained unchanged despite numerous changes in related elements of the languages. This word first appeared as part of the name ᴱQ. Mar __Vanwa__ Tyaliéva “Cottage of the Lost Play” from the 1910s (LT1/14). Its most notable use in later writings was in the poem Namárië, where it appeared in the phrase sí __vanwa__ ná, Rómello __vanwa__, Valimar! “now lost, lost to those from the east is Valimar!” (LotR/377).
Conceptual Development: In the Qenya Lexicon of the 1910s, the adjective ᴱQ. vanwa “gone, on the road, past, over, lost” appeared under the early root ᴱ√VAHA (QL/99), itself based on the root ᴱ√AVA “go away, depart, leave” (QL/33). It reappeared in the English-Qenya Dictionary of the 1920s with the gloss “over, gone” (PE15/76). In The Etymologies of the 1930s, ᴹQ. vanwa “gone, departed, vanished, lost, past” was derived from the root ᴹ√WAN “depart, go away, disappear, vanish” (Ety/WAN).
In the Quenya Verbal System of the 1948, ᴹQ. vanwa “gone, over” was given as an example of the perfective participle -nwa in combination with the root ᴹ√BĀ/BANA “go, proceed” (PE22/106). Very likely this was the derivation when Tolkien wrote the Namárië poem for the 1st edition of The Fellowship of the Ring published in 1954. However, in 1959 Tolkien abandoned the root √BA(N) “go” (PE17/143). At that point Tolkien coined a new etymology for vanwa based on the invertible root √WĀ/AWA, most fully described in the Quendi and Eldar essay from 1959-60 (WJ/366). In that document Tolkien described its derivation and meaning as follows:
> This last [vanwa] was an old formation (which is also found in Sindarin), and was the most frequently used part of the verb [auta- “go away, leave”]. It developed the meanings “gone, lost, no longer to be had, vanished, departed, dead, past and over”.
Despite all these changes in its derivation and the associated roots, the adjective vanwa itself retained the same basic form and meaning throughout Tolkien’s life.
-nwa is said to be "a passive suffix" irregularly occurring in the word vanwa "lost" (PE17:63), the word seems to be irregular since the underlying root means "go away" and so vanwa is in a sense a past active participle, *"having gone". Compare PE17:68.