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.
uith
adjective. both
och
noun. egg
A word appearing as G. och “egg” in the Gnomish Lexicon of the 1910s (GL/62), likely based on the early root ᴱ√OHO from which Qenya “egg” words were derived (QL/69). It has a somewhat unusual plural form uith, likely from primitive ✱oχ-þ- as suggested by Roman Rausch with the vocalization of *oχ* to *oi* which then became *ui* (HPG/§2.8).
Neo-Sindarin: I’d retain ᴺS. och “egg” for purposes of Neo-Sindarin based on a Neo-Root ᴺ√OKH, but I’d give it a more normal Sindarin plural: ych “eggs”.
athwi
adjective. both
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 for “both” in the Gnomish Lexicon of the 1910s related to G. gwi- “twi-, bi-, di-”. It had variants uith, uivren, and athwi, but all these were deleted (GL/20, 74).