Early Noldorin
nui
noun. bee
fuin
noun. night
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 word appearing as ᴱN. nui “a bee” in Early Noldorin Word-lists of the 1920s (PE13/151). Its exact etymology is unclear.
Conceptual Development: In the Gnomish Lexicon of the 1910s, Tolkien gave several variant forms for “bee”: G. nio, nios or nion (the last of these was rejected), and feminine G. niwin; Tolkien also considered but rejected nios as a feminine form (GL/60). The base forms nio and nios were derived from primitive ᴱ✶nēgu and ᴱ✶nēgis respectively, most likely from a variant of the early root ᴱ√NEHE which was the basis for “honey” and “bee” words in the contemporaneous Qenya Lexicon (QL/65). Early Noldorin Word-lists of the 1920s had ᴱN. nui as mentioned above, as well as an unglossed word ᴱN. niw which might be a variant (PE13/151).
Neo-Sindarin: In Tolkien’s later writings, the root √NEG “ooze, drip” was still connected to “honey” (PE19/91). Thus I think primitive ✱nēgū might still be viable as an ancient word for “bee”, which would most likely become ᴺS. nîw in Neo-Sindarin after ancient <em>ē</em> became <em>ī</em>. Compare S. lhaw “ears” from ancient dual ✱slasū for an example of how the final u would become diphthongal after the loss of an intervening weakened consonant, thus: ✱nēgū > ✱nīɣu > nīu̯, spelled nîw.