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.
nîlûmasculine name. (Man in the) Moon, Moon