Finnish strongly influenced J.R.R. Tolkien’s creation of Quenya.
Quenya is one of Tolkien’s Elvish languages, and its sound patterns and grammar were especially influenced by Finnish. Tolkien encountered Finnish while studying languages and was impressed by the structure and beauty of the Finnish national epic, the Kalevala. He adapted inspiration from Finnish without simply copying the language.
Quenya also reflects Tolkien’s broader knowledge of historical and constructed languages. Its vocabulary and history within Middle-earth were developed as part of the mythology, including the distinction between High-elven Quenya and other Elvish tongues such as Sindarin.
Finnish is therefore the best single answer to the question of Quenya’s strongest real-world linguistic influence. Welsh is more closely associated with Sindarin’s sound inspiration, while Latin and Gothic contributed to Tolkien’s wider linguistic interests but are not the primary answer for Quenya.