When Caesar said "The die is cast" as he crossed the Rubicon River with an army, he was essentially saying that he was taking a chance. Id est: His action was analogous to throwing a a cube with numbers on its faces hoping for a favorable number because his action signaled an intent to depose the then current Roman emperor & would result in his execution if he failed. When I was in 7th or 8th grade & raised with an early knowledge of metallurgy, I interpreted his statement as saying he was committed to deposing the current emperor. It was analogous to creating a forging die which could only be used to make one particular shaped metal product. A girl friend of mine was aware of the term casting a dye, which meant making a white piece of cloth a particular color & viewed Caesar's statement as analogous to dying a piece of white cloth after which it would be difficult to change back to white or dying it another color (other than black). It is interesting that the above three interpretations seem to suggest the same meaning.