In chess when a player castles they swap Rook with King (Trump with military). Rooks are considered endgame pieces, hence they are major pieces as opposed to minor. Castle Rock could be interpreted as both, Castle Rock Entertainment and Castle Rook, the swap, a play on words.
This theory may have already been discussed, but if we are playing 4D chess, then the endgame would be a chess move... a move no one saw coming until now.
Personally, I hope they "Castle" the Capital right out of DC, over to Texas or elsewhere, and let the Supreme Court rock on over there too; minus Roberts it might be nearly legit.