A totally fictional character, invented by J.R.R. Tolkien. There is no one-to-one matchup of LOTR characters or events with Catholicism.
One can see in the figure of Tom Bombadil echoes of Christian souls such as St. Francis of Assisi, whose experience of God had a directness and simplicity outside societal norms and intellectual structures. See G.K. Chesterton's biography.
On the other hand, Tolkien had many other historic and literary influences other than the Catholic Faith. Someone with more knowledge of the subject than I might find a source for the character within the English and Scandinavian historical and mythological traditions in which Tolkien specialized.
Tom could also be seen as a kind of pure hermit; he doesn’t generally involve himself with the affairs of others, and maybe because of that the ring has no effect on him.
Anyway, in one of the letters, Tolkien plainly tells his son "Gandalf was an angel."
Cheers!