√PĀ/APA root. “touch; after, behind of place”
This root and ones like it were used for various spacial and temporal relationships during Tolkien’s life. Perhaps the earliest iteration in this chain of developments was the root ᴱ√PE “at, by” from the Qenya Lexicon of the 1910s, with derivatives like ᴱQ. penasta “being near at hand, support, backing” and ᴱQ. peanta- “give into one’s hands, give instructions to, enjoin” (QL/72). In Noldorin Word-lists from the 1920s Tolkien gave primitive ᴱ✶apa > ᴱN. ó “to, on” and ᴱT. pa, presumably of the same meaning (PE13/151). In a late note of unclear date Tolkien wrote:
√apa “touch” (not with fingers but of the contact of surfaces, esp. vertical surface). So prep. apa, pa “touching, against”. In Q. this, espec. in form pā̆ is used as prep. = touching, as regards, concerning. Also the verb ape is used fig. as to touch one, concern, affect. In literal sense [touch] the strengthened weak verb appa is mostly used (VT44/26).
In another note from this period Tolkien glossed apa as “above but touching” (VT44/26).
In other words from the 1950s and 60s, apa- is given the temporal sense “after”, most notably in Q. Apanónar/S. Abonnen “After-born” (WJ/386-387), the former appearing in the published version of The Silmarillion (S/103). It was also used temporally in Q. apacenyë “of foresight” (MR/216). In a table of spatial and temporal roots from 1969, Tolkien gave √PĀ/PATA “after, behind of place” (PE22/147) and in another 1969 note Tolkien glossed apa, pā as both “before of time” and “after (later than)”, with both being deleted (VT44/36). Other similar roots in the semantic space of “after” include √EPE and √OPO.
Neo-Eldarin: As indicated by the discussion above, Tolkien’s treatment spatial and temporal prepositional elements was wildly inconsistent. √APA was one of the elements Tolkien used for “before” and “after”, but also as “on” or “touching”. For purposes of Neo-Eldarin, the most useful definition of √PĀ/APA is “touch”, for which we have no other good late roots, so I would assume this was its primary meaning. I generally prefer ✶epe for “after (of time); before (of space)” and ✶nō for its opposite. However, I think apa- might be a euphonic variant of epe-, perhaps limited to “after” of time, to justify Q. Apanónar/S. Abonnen “After-born”.
References ✧ PE22/147; VT44/26
ᴱ✶apa prep. “to, on”
Reference ✧ PE13/151 ✧ “to, on”