Tom Bombadil from The Hobbit and Lord of the Rings
The most significant fact about Tom Bombadil is the statement by Gandalf that should the dark Lord repossess the Ring of Power, Tom Bombadil would be the last to fall to his influence, but even he would eventually fall. He had the greatest power to resist the Dark Lord.
Who or what was Tom Bombadil?
From: The Tolkien FAQ by William D.B. Loos
This question has been a widely debated, sometimes far too vehemently. Part of the difficulty is the complexity of Tom's literary history. Tom was originally a doll (with blue jacket and yellow boots) owned by Tolkien's son Michael. The doll inspired a story fragment, such as he often invented for his children's amusement. That fragment was in turn the basis for the poem "The Adventures of Tom Bombadil", published in 1933, which also introduced Goldberry, the barrow wights, and Old Man Willow (the poem was the source of the events in Chapters 6 through 8 of Book I). In a contemporary letter (1937) Tolkien explained that Tom was meant to represent 'the spirit of the (vanishing) Oxford and Berkshire countryside'.
(The Letters of J.R.R. Tolkien, no 19)
Tolkien introduced Tom into The Lord of the Rings at a very early stage, when he still thought of it as a sequel to the The Hobbit, as opposed to the The Silmarillion (the tone was changed during the first chapters of The Lord of the Rings). Tom fit the original (slightly childish) tone of the early chapters (which resembled that of the The Hobbit), but as the story progressed it became higher in tone and darker in nature. Tolkien later claimed that he left Tom in he decided that however portrayed Tom provided a necessary ingredient (see last paragraph). Some very cogent reasons are produced in a couple of wonderful letters.
(The Letters of J.R.R. Tolkien, 144 & 153)
As to Tom's nature, there are several schools of thought.
He was a Maia (the most common notion). The reasoning here is plain: given the Middle-earth cast of characters as we know it, this is the most convenient pigeonhole in which to place him (and Goldberry as well) (most of the other individuals in The Lord of the Rings with "mysterious" origins: Gandalf, Sauron, Wizards, and Balrogs did in fact turn out to be Maiar).
He was Ilúvatar. The only support for this notion is on theological grounds: some have interpreted Goldberry's statement to Frodo (F: "Who is Tom Bombadil?" G: "He is.") as a form of the Christian "I am that am", which really could suggest the Creator. Tolkien rejected this interpretation quite firmly.
T.A. Shippey (in The Road to Middle-earth) and others have suggested that Tom is a one-of-a-kind type. This notion received indirect support from Tolkien himself:
(The Letters of J.R.R. Tolkien, p. 174)
"The story is cast in terms of a good side, and a bad side, beauty against ruthless ugliness, tyranny against kingship, moderated freedom against compulsion that has long lost any object save mere power, and so on; but both sides in some degree, conservative or destructive, want a measure of control. But if you have, as it were taken 'a vow of poverty', renounced control, and take delight in things for themselves without reference to yourself, watching, observing, and to some extent knowing, then the question of the rights and wrongs of power and control might become utterly meaningless to you, and the means of power quite valueless."
(The Letters of J.R.R. Tolkien, p. 178).
(The Letters of J.R.R. Tolkien, p. 179).