In about twelve hours the Cardinals of the Catholic Church -- all those under 80, with the exception of a very few -- will walk in procession into the Sistine Chapel and sit in red-robed rows beneath Michaelangelo's great ceiling. They've been debating and discussing -- polite terms for politicking -- for days now, and this is it. They'll vote as many ballots as they have to, one each morning and afternoon, returning to their rooms at night, until they have a Pope.

"Conclave" is from the Latin for "with a key." This is not the same as "with a clue," but I digress. This term for the gathering of Cardinals that elects a Pope comes from the time in the 13th C. when after eighteen Popeless months the city fathers of Viterbo locked the Cardinal-electors in, fed them only bread and water, and finally removed the roof of the Palazzo di Papi and made them stay there until they had a Pope. That Pope, Gregory X, thought all this was such a great idea that he made it a law that henceforth the Cardinal-electors should be locked in until a Pope was chosen. They feed them better now, though, and no one's removing the Sistine Chapel roof.

"Conclave," the above notwithstanding, has a rather different meaning in BLOOD OF THE LAMB, where Sam Cabot uses it to refer to a gathering of... rather different people.