J.R.R. Tolkien used Finnish as a major basis for the name and structure of Quenya.
Quenya is one of Tolkien’s principal Elvish languages. He developed it as part of a connected family of invented languages, drawing on his professional knowledge of historical linguistics and on languages he admired. Finnish had a particularly strong influence on Quenya’s sound and grammar.
Tolkien did not simply copy Finnish vocabulary. He adapted selected features while creating an independent language with its own history, speakers, dialects, and relationship to other languages in his mythology. Quenya is associated especially with the High Elves and is often compared with Latin in its elevated literary role.
Sindarin is another major Elvish language, but Tolkien based much of its sound and development on Welsh rather than Finnish. This distinction is a frequent source of confusion when discussing Tolkien’s language construction.