The usual word for “and” in the 1910s was ᴱQ. ya(n) (PE15/69, VT40/8). It was derived from the early root ᴱ√YA (or possibly ᴱ√(D)YṆTṆ) in the Qenya Lexicon of the 1910s (QL/104-105). In his later writings, the usual word for “and” was Q. ar, but something like ya(n) survived in the “dual” conjunction yo “both ... and”.
Early Quenya
are
adverb. beside, along
are
adverb. very, intensive
are-
prefix. intensive
ar váro naltur an ómi karmar
*but rather they are to all deeds
néri ur natsi nostalen máre
*men are not beings good by nature
piliningwe súyer nalla qanta
*the airs are so full
qentien no máre nar i hondor
*than good, I said, are the hearts
var limpilto var túkielto
*they are bound to or have looked for
ari-
prefix. intensive
kale
noun. day
aka
adverb. very, intensive
aka-
prefix. intensive
lá
noun. day
ole-
prefix. intensive
oli-
prefix. intensive
olóle
very, intensive
sa-
prefix. intensive
ya(n)
conjunction. and
The adverb ᴱQ. are “beside, along” appeared in the Qenya Lexicon of the 1910s under the early root ᴱ√ƷARA “spread, extend sideways” (QL/32).
Neo-Quenya: Since the preposition ar(a) “beside” appeared in Tolkien’s later writings, I think ᴺQ. arë “beside, along, ✱near” can be retained as an adverbial form of that preposition.