In the Styx

In The Amazing Adventures of Kavalier and Clay, Michael Chabon uses the idiom "out in the sticks", meaning "in the boondocks", "in the middle of nowhere". According to EtymOnline, this idiom arose around 1905, simply from the meaning of sticks as in trees as in a rural place.

I've heard the phrase plenty of times, but this must be the first time I've seen it (or at least first time I've noted it) in print. Without really thinking about it, my mental image of this phrase had always been "out in the Styx". Which of course, now that I actually think about it, seems pretty unlikely. Definitely more fun my way though...