Gnomish
nogin
noun. boy, lad, urchin
gontha
noun. boy
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun appearing as G. nogin “boy, lad, urchin” in the Gnomish Lexicon of the 1910s (GL/61); its derivation is unclear since no nearby words seem to be related, but it could be a variation on G. naug “a dwarf” (GL/59).
Neo-Sindarin: I think this word may be salvageable as Neo-Sindarin ᴺS. nogen, reinterpretted as a derivative of the root √NUK “stunted”, originally an adjective ✱nukina used to refer to short persons or children in a less-than-flattering way. Given its glosses, I would use this word mainly for a mischievous or irritating male child; for a more ordinary word for “boy”, I’d instead use S. ion(n).