J.R.R. Tolkien studied Finnish and used it as a basis for Quenya.
Quenya is one of Tolkien’s best-developed Elvish languages. Its sound and grammar were influenced strongly by Finnish, while its vocabulary and fictional history were created within Tolkien’s own mythology.
Tolkien encountered Finnish through the Kalevala, Finland’s national epic. He admired its structure and described discovering Finnish as producing a powerful aesthetic impression. Quenya was not simply Finnish with substituted words; it was an original constructed language with its own historical development inside Middle-earth.
Welsh also influenced Tolkien, especially the sound of Sindarin. This distinction causes frequent confusion: Finnish is most closely associated with Quenya, while Welsh is a major influence on Sindarin.