Uinen (Uinend-, as in dative Uinenden) fem. name, used of a Maia, spouse of Ossë (UY, NEN). Adopted and adapted from Valarin (WJ:404), though it is also said that it contains -nen "water" (SA:nen); the latter explanation may be folk etymology. In the Etymologies, the name is derived from the same stem (UY) as uilë "long trailing plant, especially seaweed".
Quenya
nendo
noun. water mead, *watered plain
nen
noun. nostril
Nénar
water
Uinen
water
nén
water
nén (nen-) noun "water" (NEN).
nén
noun. water, water, [ᴱQ.] river
The word for “water”, a derivative of the root √NEN of the same meaning (PE17/52; Ety/NEN). Its stem form was nen- (Ety/NEN) and its primitive form was given as ✶nē̆n, the vowel length variation due to distinct subjective nēn versus objective/inflected nĕn- in ancient monosyllables (PE21/64).
Conceptual Development: This word first appeared in the Qenya Lexicon of the 1910s with two senses: “river” and (archaic) “†water”. Tolkien indicated the two senses were based on distinct roots: ᴱ√NEŘE [NEÐE] and ᴱ√NENE respectively, with two distinct stem forms nend- and nēn (QL/64-65). The Poetic and Mythological Words of Eldarissa also mentions the forms nen (nēn-) “water” versus nen(d-) “river” (PME/64-65). In the English-Qenya Dictionary of the mid-1920s Tolkien had both nēn “river” (PE15/76) and nēn “water” (PE15/78), but in the Early Qenya Grammar he had only nēn “water” (PE14/43, 72), also appearing as nen “water” in documents on The Valmaric Script from this period (PE14/110).
In the Declension of Nouns from the early 1930s, Tolkien had ᴹQ. nēn “water”, but in this document it had nēn- with long ē in its inflected forms as well (PE21/23). In The Etymologies of the 1930s, however, uninflected nén “water” had a stem form of nen- with short e (Ety/NEN), and the reasons for this variation was discussed in Primitive Quendian Structure: Final Consonants from 1936, the nominative/objective distinction noted above (PE21/64). This seems to be the paradigm Tolkien stuck with thereafter, as evidenced by S. nen “water” rather than ✱✱nîn.
Nénar noun name of a star (or planet), evidently derived from nén "water" (Silm), tentatively identified with Uranus (MR:435)