Gandalf, Odin, and the Wolf's Belly (FR 2.iv.298)

At Ragnarök the monstrous wolf, Fenrir, will swallow Oðinn, some of whose attributes Tolkien drew on in envisioning Gandalf, whom he saw as an 'Odinic wanderer' (Letters, no. 107).¹  Gandalf shows this in The Lord of the Rings, as Marjorie Burns points out, 

by wearing a broad-brimmed hat and carrying a walking staff, as the wandering Odin does, though Gandalf's association with eagles, his enmity with wolves, and his ownership of a nearly supernatural horse add to this as well.²

All of which leads me to think that Sam's remark when the Company is being menaced by wolves is a joke on Tolkien's part:

'My heart's right down in my toes, Mr. Pippin,' said Sam. 'But we aren't etten yet, and there are some stout folk here with us. Whatever may be in store for old Gandalf, I'll wager it isn't a wolf's belly.' 

(FR 2.iv.298)

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¹ See John Lindow, Norse Mythology: A Guide to Gods, Heroes, Rituals, and Beliefs, Oxford (2001) 111-14, 247-52, 254-58.

² Marjorie Burns, Norse and Christian Gods: The Integrative Theology of J. R. R. Tolkien, in Tolkien and the Invention of Myth: A Reader, ed. Jane Chance, The University of Kentucky Press (2004) 168; Marjorie Burns, Gandalf and Odin in Tolkien's Legendarium, edd. Verlyn Flieger and Carl Hostetter, Greenwood Press (2000) 219-31. Gandalf, however, would have balked at the claim that he owned Shadowfax, a horse that carried riders only by his own consent. In Perilous Realms: Celtic and Norse in Tolkien’s Middle-earth, University of Toronto Press (2005) Burns rightly notes that Odin's fate is hinted at in Sam's words, but overlooks their humor.