Gnomish
eng
noun/adjective. smooth, level
eng(a)
noun. plain, vale
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 in the Gnomish Lexicon of the 1910s given as enga “plain, vale” (GL/32). It also appeared in the Name List to the Fall of Gondolin as eng “a plain or vale” (PE15/24). It was probably derived from the early root ᴱ√EŊE from Qenya Lexicon which had derivatives like ᴱQ. endl “plain, vale” (QL/36).