I've heard the claim that Tolkien wrote, or at least started writing, The Lord of the Rings to support (with a history providing cultural depth) the artificial languages he was creating at the time.
Is this true, or was it the other way round? Which came first, the languages or the fiction?
Tolkien began creating languages when he was a young man, well before he started his career as an author. This essay shows that the languages came first and that his talent as a linguist led to his desire to create worlds in which these languages were commonplace.
Tolkien started writing the legendarium to support his constructed languages, then came The Hobbit, a children's story with the lengendarium as its (distant) background. The publishers of The Hobbit asked Tolkien to work on a sequel and that's what became The Lord of the Rings.
The legendarium is what Christopher Tolkien edited together to form The Silmarillion.
If I recall correctly, J.R.R.Tolkien loved both Welsh and Finnish and tried to construct a linguistic history that would explain a Welsh-like and Finnish-like language (Sindarin and Quenya respectively) that had a common origin.
Tolkien once said that the reason he created Arda was because he needed a world in which the word Earendil would come to its right. There's some great material on YouTube about this:
Christopher Tolkien on his father's languages
A must see 3-part lecture: J.R.R. Tolkien: An Imaginative Life
The languages came first.
J.R.R Tolkien was s philologist, and he loved languages. So he started creating a few himself. After a while, I suppose he realised these languages could be used, and he created a world (Middle Earth) and, for it, characters to speak the languages.
