the die is cast

Etymology:

• From games of chance in which the outcome is determined by the throwing of dice or a single die. Popularized by its use by Suetonius when Julius Caesar crossed the Rubicon to begin a civil war in the Roman Republic, indicating the commission of an irreversible act, whence also cross the Rubicon.
• The form “the die is cast” is from the Latin iacta ālea est, a grammatically incorrect translation by Suetonius, 121 CE, of the Ancient Greek phrase of Menander ἀνερρίφθω κύβος, which Caesar quoted in Greek. The Greek translates rather as “let the die be cast!”, or “let the game be ventured!”.