To say
the die is cast is to suggest that a process is past the point of return. In the metaphorical phrase,
die refers to a numbered cube used in gaming (the singular of
dice), and
cast means
thrown.
The phrase is attributed to Julius Caesar, who reportedly said it (in Latin) as he crossed the Rubicon river with one of his legions to start the civil war that would bring him to power. The Rubicon was the northern border of the Roman republic, and Caesar was not in a position to legally command soldiers within Rome. As the offense was punishable by death, victory was his only option. When he said “the die is cast,” he meant he’d made his play and there was no going back.
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