Finnish was a major inspiration for J.R.R. Tolkien’s Quenya language.
Tolkien studied Finnish and admired its structure, sound, and rich inflection. He used those impressions when developing Quenya, the language associated with the High Elves and often described as an elevated or ceremonial Elvish language.
Quenya was not Finnish with renamed words. Tolkien constructed it as an independent fictional language with its own vocabulary, grammar, history, and relationship to other languages in his legendarium. The influence is therefore literary and linguistic rather than a direct translation system.
Welsh also influenced Tolkien, particularly in the development of Sindarin. Latin and Greek contributed to his broader philological interests, while Old Norse and Old English influenced many names and narrative elements. These influences make it important not to treat every Elvish language as having the same source.