Gunsang: I thought Rugby was developed after Association Football, but I could be wrong.
DukeNukemForever: Or maybe that way ;-) I only remember that there was a split up between the two, because one group wanted to use their hands with a closer and tougher gameplay while the others preferred a cleaner play using only the foot.
I believe that the term football came into use a while before the split, but again I could be wrong. Anyone care to fact check?
Rugby was originally called football rugby, while football was called football association (and still is, but everybody just uses football instead).
Rugby also predates football by about 20 years, although it's kind of hard to tell since there were games pretty similar to it, except without all those pesky rules.
From what I read in a book about football's history, it was actually an Anglican priest who taught in a school who developed football, because he felt rugby was too violent.