Gnomish
ivrin
adjective. fertile
glint
noun. crystal
sincli
noun. crystal
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
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.