It's a common observation in Lie theory that Cartan matrices and the Killing form are named after the wrong people; they were discovered by Killing and Cartan, respectively.  I remember learning about many other examples of this phenomenon, but can't think of too many at the moment.  Wikipedia has <a href="http://en.wikipedia.org/wiki/List_of_examples_of_Stigler%27s_law">a short list</a>, but I'm curious about more obscure examples.  So I thought I'd ask MO for a nice list.  

Bonus points for an interesting story behind why the concept was incorrectly named.  Concepts that were deliberately named in honor of another mathematician don't count.