@@@ es might be an assimilated form as suggested by Helge Fauskanger (QQ/es)
Qenya
enta
that yonder, then (fut.)
entarda
place name. Thither Lands, Middle-earth, Outer Lands, East
entare
proper name. Year’s beginning
enar
noun. tomorrow
en
there, yonder, far away; look yon(der); that; in that (future) case
tasse
adverb. there
A name for the lands of the East in The Etymologies from the 1930s, also appearing as Entar (Ety/EN). It is apparently a compound of enta “that yonder” and arda “region”. Oddly, it was also glossed “Middle-earth”, though The Etymologies had plenty of other names with that meaning.