J.R.R. Tolkien based the fictional language Quenya largely on Finnish.
Quenya is one of Tolkien’s most developed Elvish languages. Its sound and grammar were strongly influenced by Finnish, while its vocabulary and history belong to Tolkien’s invented world. In Middle-earth, Quenya was associated especially with the High Elves and was used as a formal or historical language.
Sindarin, another major Elvish language, drew more heavily on Welsh. Tolkien was a professional philologist, so his invented languages were designed with sound changes, grammatical structures, and historical relationships rather than as random collections of words. Quenya is sometimes called “High-elven” in Tolkien’s writings.