Gnomish
ivrin
adjective. fertile
failivrin
feminine name. *Sheen of Ivrin
glint
noun. crystal
sincli
noun. crystal
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.
An adjective appearing as G. ivrin “fertile” in the Gnomish Lexicon of the 1910s related to G. gav- “produce, bear fruit” (GL/52), derived from the early root ᴱ√ẎAVA (QL/105).
Neo-Sindarin: I would update this word to ᴺS. iavren “fertile” based on the later form of the root ᴹ√YAB (Ety/YAB). Based on its etymology, I would apply this word to both fertile fields as well as fertile people.