Finnish inspired much of J.R.R. Tolkien’s fictional Elvish language Quenya.
Tolkien admired Finnish grammar and vocabulary, and Finnish became a major influence on the sound and structure of Quenya. He encountered the language through the Finnish national epic Kalevala, whose style and mythology also affected his imagination.
Quenya was not simply Finnish with invented words. Tolkien developed it as a constructed language with its own history, grammar, vocabulary, and relationship to other languages in his legendarium. He imagined it as an ancient, formal language associated especially with the High Elves.
Sindarin, another major Elvish language, was influenced more strongly by Welsh. This distinction is useful because “Elvish” is not one single language in Tolkien’s works; several related or historically connected languages appear across the mythology.