Perfect - that's the exact quotation I was thinking of, too!
It's the troll from 'Perry-the-Winkle.'
The hobbit connection is the hobbits in the poem, and the fact that Bilbo probably wrote it, (I think). (Although thinking about it, it mentions the Lockholes, which I am not sure existed as such before around the Scouring, so maybe Sam wrote it?)
I said a 'living thing,' although I suppose the characters in the poem are fictions *within* Tolkien's fiction.