A lake near Eldalondë “so named from the abundance of sweet-smelling shrubs and flowers that grew upon its banks” (UT/168). This name might be a compound of the verbal element nis- (“to smell sweetly”?) seen in nísima “fragrant” and the noun nén “water”, therefore meaning something like “✱Fragrant Water” (as suggested by Helge Fauskanger, QQ/Nísinen).
Quenya
Nísinen
fragrance-water
nísinen
place name. *Fragrant Water
Elements
Word Gloss nis- “*to smell sweetly” nén “water, water, [ᴱQ.] river”
Nísinen noun *"Fragrance-water", a lake in Númenor (UT:168)