Here's the list of the 50 words found most puzzling by readers of the New York Times. I take no particular pride in declaring that I am (perhaps too) comfortable with all 50--I worked to expand my vocabulary when I was young and the curse of pretentiousness has hung over me ever since. I don't really use louche, #3, very often, except perhaps when talking about Winston Churchill's friends. I know #46, phlogiston only because I had the great good fortune to take a course in the history of physics from Al Stewart at Antioch College back in the early 50s (I met him a few years later; he didn't remember me). I get far too much enjoyment out of #11 schadenfreude. I don't think I use #29 risible much at all, which is surely just as well.
But #31 swine? Well, they do say that New York is a parochial town.