Hub is an archaic word for the nave of a wheel, the hilt of a weapon, or the mark aimed at in quoits. If a cart sinks in the mud up to the hub, it can sink no lower; if a man is thrust through with a sword up to the hub, the entire sword has passed through him; and if a quoit strikes the hub, it is not possible to do better. Hence the phrase means fully, entirely, as far as possible. It is not American, but archaic English. (See Hub.)
“I shouldn't commune with nobody that didn't believe in election up to the hub.” —Mrs. Stowe: Dred, vol. i. p. 311.