The House is up. The business of the day is ended, and the members may rise up from their seats and go home.
A.B. is up. A.B. is on his legs, in for a speech. “Up, Guards, and at them!” Creasy, in his Fifteen Decisive Battles, states that the Duke of Wellington gave this order in the final charge at the battle of Waterloo. It has been utterly denied by recent writers, but it is the fashion to deny or discredit all cherished traditions. I, for one, wish the tradition were true, because, like Nelson's mot at Trafalgar, it gives a memorable interest to the charge; but alas! we are informed that it was not the Guards, but the 52nd light infantry which broke the column of the French Imperial Guard in the final charge, and “honour to whom honour is due.”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894