“Bitsy” is an adjective all by itself in the OED. The “-y” suffix indicates “characterized or full of” and in Old English was spelled “ig”. Tolkien uses it uniquely adverbially, replacing “for a bit”, constructed from his deep understanding of the roots of our language. I’m giving it the onomatopoeia tag for adding an ‘s’ to Gollum’s words where there was none.

• 05.022 and chats with it a bitsy

“-y, suffix1.” OED Online. Oxford University Press, June 2015. Web. 14 July 2015.

“bitsy, adj.” OED Online. Oxford University Press, June 2015. Web. 14 July 2015.