The belief that duels were more about honour than violence lead to a very odd case where both side's seconds loaded the duelists guns with gunpowder, but no shot.
Both men happily fired away at each other for 3 rounds and ended the duel unharmed but satisfied. Until the seconds deception was discovered, at which point the challenger challenged his own second to another duel, this time with loaded weapons.
Meaning "the die is cast", and originally given as "iacta alea est", this is the phrase Suetonius ascribes to Julius Caesar as he led his armies across the Rubicon in 49BC. By this act he defied the senate and started his long civil war against Gnaeus Pompeius Magnus and the Optimates (the supporters of the senate's ongoing authority). It is a phrase used to indicate passing a point of no return or committing an irrevocable action.