A word for “fly” in the Gnomish Lexicon of the 1910s (GL/68), perhaps related to the early root ᴱ√ITI “peck, bite (of flies), annoy” (QL/43).
Gnomish
rib
noun. shore; stripe, line; border, fringe
sitha
noun. fly
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 in the Gnomish Lexicon appearing as G. rib along with the equivalent word G. rim “a stripe, line; border, fringe”, but rib had the added meaning “shore” (GL/64). These were clearly based on the early root ᴱ√rib [RIPI] (GL/64; QL/80).
Neo-Sindarin: I would retain ᴺS. rib for purposes of Neo-Sindarin based on the Neo-Root ᴺ√RIP, but only for the senses “stripe, line”.