From Hull AWE
- The first meaning, as far back as the fourteenth century, was 'a cube marked with dots on all six sides used for games of chance, like backgammon'. In informal speech, this is usually called 'a dice' - a misuse which annoys pedants; for an explanation, see die - dice.
- This developed into a technical term in engineering and related subjects. Here, the essential meaning of 'a die' (the plural of this is dies) is 'a mould'. This developed from the 'cube' in an interesting way, to etymologists.
- In the sixteenth and seventeenth centuries, a die was the highly valued 'master' from which coins (in softer metal) were struck. In other words, it is a kind of 'negative' of the design on the coin. When the coiner places a 'blank' (disc of metal) of the right kind between a pair of dies (one for the obverse, or 'head[s]' of the coin and one for the reverse, or 'tail[s]'), and then hits the top die with a hammer, the blank is stamped with the design on the die, and becomes a good coin.
- It was then used in the seventeenth century for a printing tool: a block (in the shape of a gambler's cube) for printing. The die had a design on it, in the reverse of the desired image, which could be transferred to the object worked on - cloth or paper - for printing.
- In general terms, a die is 'a mould', for casting various hard substances like metal, often when they are molten, sometimes when they are hard. Engineers have since the nineteenth century expanded the meaning to cover many different devices for shaping hard substances, principally metal: dies are used to cut the threads of screws, or the rifling of cannon;. Dies may be used in many operations forming metal, such as bending, extruding, curling, shaving and trimming.