My favorite fan theory I saw in a fic once was that “Blunt the Knives” is already a dwarvish drinking song with the chorus “That’s what my old mother hates” and since “Bilbo Baggins” scanned so well with it, the dwarves just adapted on the spot, rather than all of them inexplicably bursting into a brand new song
Omfg that’s perfect!!!
Aha, I found a source for it! For credit it’s at least mentioned in the Nwalin fic “Dirty Deeds (Done Dirt Cheap)” by greenkangaroo on AO3, though I imagine I must have read it somewhere else too because I never read Nwalin…