The fictional language J.R.R. Tolkien created with strong Finnish-inspired features is Quenya.
Quenya is one of Tolkien’s most developed Elvish languages. He based aspects of its sound and structure on Finnish, while also drawing on his knowledge of Welsh, Latin, Greek, and other languages. Tolkien did not invent Quenya merely as a collection of words; he created historical relationships, grammatical forms, and changes through time.
Within Middle-earth, Quenya is associated especially with the High Elves and with the ancient Elven realms of Valinor. It remains important in names, formal speech, poetry, and ceremonial language. The name of the sword Andúril, for example, comes from Quenya.
Quenya is often confused with Sindarin, another major Elvish language. Sindarin became the everyday Elvish language of many Elves in Middle-earth and was influenced strongly by Welsh. Khuzdul is the secret language of the Dwarves, while the Black Speech was created for the servants of Mordor.