Elves and dwarves didn't strictly mean children's fairy tales prior to Tolkien. There's plenty of semi-popular prior art where they feature, like the Worm Ourob

Elves and dwarves didn't strictly mean children's fairy tales prior to Tolkien. There's plenty of semi-popular prior art where they feature, like the Worm Ouroboros or The King of Elfland's Daughter. Poul Anderson also published The Broken Sword the same year as LOTR, which shows a lot of the same influences as written by a very different author. Tolkien's importance is that the specific kinds of creatures he wrote became the default for virtually all subsequent authors and the popularity/quality of the works were pivotal in establishing fantasy as a "proper" genre.