The Chapter 16 instance of “splutter” occurs when Bilbo stumbles and falls into a stream on his super-silent mission to reach Bard without the dwarves’ knowledge.  Definitely a funny bit of slapstick.  Johnson (of “Boswell’s Life of___” fame) called this a low word, and I’ll happily take that evidence.

• 05.041 and spluttered.
• 05.073 and spluttered
• 08.109 so now they all began to splutter
• 08.123 and spluttered
• 09.055 He came up again spluttering
• 16.017 shivering and spluttering,

“splutter, n.” OED Online. Oxford University Press, March 2015. Web. 20 May 2015.