Jonah, I don’t think “federalism” today means the opposite of what it meant in 1787. It only seems that way because of what my old colleagues in the philosophy department would call the “context of utterance.”
It’s a little like the verb “cleave,” which has the apparent linguistic distinction of being its own antonym:
1. Split or sever (something), esp. along a natural line or grain.
2. Stick fast to: “Rose’s mouth was dry, her tongue cleaving to the roof of her mouth”.
But in fact, the two definitions of “cleave” are easily reconcilable when one pays attention, not to the stuff that is being alternately “severed” or “stuck fast to,” but to the thing that is doing the severing or the sticking-fast-to. Take a butcher’s cleaver to a fresh and bloody 20lb rump roast and you’ll find that the knife cleaves the meat in the first sense while the meat cleaves to the knife in the second. When you attend closely to the matter, you realize that the concept common to both senses of “cleave” is that “natural line or grain” bit, and that whether one is putting-together or taking-apart along that seam is secondary. This is one of the many, many, many things I love about cleavage.
So it is with “federalism.” Then as now, federalism means the sharing of sovereignty between the states and the union. What changed, I think, is that in 1787 it was scandalous to suggest that the national government should have both the institutional authority and real-deal power to trump the states on key issues. In 2013, it’s scandalous to suggest that the states retain any sovereignty at all. But when John Adams called for federalism he was calling for exactly the same arrangement and as you and I are. Only we’re calling for it from through the looking glass.