A noun translated as “moon” and fully declined as an example of a Strong II noun (SD/431). It appears with both a short and long final -u, but Tolkien indicated that the form with long û is actually the personified form Nîlû “Man in the Moon” (SD/426), perhaps the Adûnaic name of Tilion. Tolkien also listed the “later forms Nil, Njūl” (SD/306), one of which may be the Westron word for “moon”, most likely Wes. nil. Andreas Moehn suggested (EotAL/NUL) that this noun may be related to nûlo/nûlu/nâlu, but given the evil connotations of these words (SD/306) and the different stem vowels, this seems unlikely to me.
References ✧ SD/241, 306, 426, 428, 431; SDI2/Nîlû
|†nīlat||dual; archaic-strong-dual||✧ SD/431|
|nīluwāt||dual subjective||✧ SD/431|
|†nīlāt||dual subjective; archaic-strong-dual||✧ SD/431|
|nīlīya||plural subjective||✧ SD/431|
|nīlō||subjective||“moon”||✧ SD/426; SD/428|