A noun in the Gnomish Lexicon of the 1910s glossed “a dale” (GL/72), probably a derivative of the early root ᴱ√TUM(B)U as suggested by Christopher Tolkien (LT1A/Tombo; QL/95).
Gnomish
glith
noun. dale, hillslope
tumli
noun. dale
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 glossed “dale, hillslope” derived from ᴱ√nḷđ (GL/40). Its plural was glidhin, indicating a stem form of glidh-. The ancient initial nḷ- developed into nli- as often happened with favored clusters like nl-, which eventually developed into dl- and then gl-. Meanwhile, the final -dh became -th, though the dh was preserved in the plural form as noted above.