J.R.R. Tolkien developed Quenya with strong inspiration from Finnish.
Quenya is one of the major Elvish languages in Tolkien’s mythology. Tolkien admired the structure and sound of Finnish, and Finnish influence is especially visible in Quenya’s grammar and phonology. He also drew on Latin and Greek, while reshaping the language to fit the history of his invented world.
Within Middle-earth, Quenya is associated especially with the High Elves and with the ancient traditions of Valinor. It functions in the stories rather like a prestigious, classical language, while Sindarin is more widely spoken among many Elves in Middle-earth.
Quenya is not simply Finnish with changed vocabulary. Tolkien constructed it as an independent language with its own roots, grammatical history, and internal development. His interest in language creation was central to his fiction, rather than an accessory added after the stories were written.