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.
place name. Thither Lands, Middle-earth, Outer Lands, East
Ethrenn“Outer Lands, East” ✧ Ety/EN
Word Gloss enta “that yonder, then (fut.)” arda “realm, region”
- Entar/Entarda ✧ Ety/EN