An adjective given as N. nenn “watery” in The Etymologies of the 1930s, derived from primitive ᴹ✶nendā (Ety/NEN).
Neo-Sindarin: In keeping with the idea that the sound “remained nd at the end of fully accented monosyllables” in Sindarin (LotR/1115), I would represent this word as ᴺS. nend in Neo-Sindarin.
From a passage inadvertently omitted from the published version of The Silmarillion (LR/301), this name is a combination of eithel “fountain” and nínui, apparently an adjective meaning “✱tearful”.