Earliest Elvish name for the Gladden Fields appearing in Lord of the Rings drafts from the 1940s (TI/114), a combination of palath “iris” and a plural (possibly Ilkorin) form of lhad “plain”, as suggested by Roman Rausch (EE/2.8).
Sindarin
loeg ningloron
place name. Gladden Fields
possibly Nandorin given genitive form -on as in Caras Galadon