“Eyebrows” appear five times in The Hobbit, and four of those times they are bushy.

• 01.008 But Gandalf looked at him from under long bushy eyebrows
• 01.100 and stuck out his bushy eyebrows,
• 06.024 He gave Bilbo a queer look from under his bushy eyebrows,
• 07.038 with his bushy black eyebrows.
• 08.107 and eyebrows,

Three times they are Gandalf’s eyebrows, once Beorn’s and once Fili’s.  I find it interesting that eyebrows are mentioned only in the first half of the book – surely Gandalf looked gruffly out from under them when he was camped with Bard, surely someone’s got singed in the dragon-attack.  I’m having an idea.

I’ve read general agreement that the tone of The Hobbit changes around chapter 10.  I hypothesize that the moment when Thorin says

• 10.020: “I am Thorin, son of Thrain, son of Thror”

is the inflection point in the theoretical graph of changes in diction in this work.  I believe that eyebrows are funny, particularly bushy ones, and their comic value keeps them unmentioned in the higher-register second half of the book. Not that Tolkien sat himself down with a list of funny words and said, “None of you shall appear after Barrels Out of Bond!” but that they simply weren’t the right tools for the job after that point.  I take it upon myself to make the theoretical graph a reality – those who know me know I am unable to resist!