Theorems' names that don't credit the right people
Wikipedia has an article on everything: List of misnamed theorems.
Obviously this list is incomplete without Stigler's law of eponymy, stipulating that no scientific discovery is due to the person it is named for, and which, according to Stigler, is due to Robert K. Merton.
http://en.wikipedia.org/wiki/Stigler%27s_law_of_eponymy
[I know this is not a theorem. We have "eponysterical". Has anyone coined "ironymous" or "erronymous"?]