Gnomish
canthil
proper name. Canthil
cantrib
noun. square
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.
The Gnomish Lexicon of the 1910s had G. cantrib “a square”, a combination of G. cant “four” and G. rib “line” (GL/25).
Neo-Sindarin: For purposes of Neo-Sindarin I would update this to ᴺS. canthil “square” as a combination of can(ad) “four” and till “point”, analogous to [N.] nelthil “triangle”.