If you have a die (a casting for example), does it have a plural? So would I have two die?, or two dies? My guess would be two die in the sense that 'die' is singular or plural, so it is like the word baggage.
But... I've also heard people call two die, dice. Which is probably a mishearing of dies.
In terms of a dice (the the square gaming thing you roll), the plural is die. But this is often confused since I hear people say roll the dice when they have two in their hand. I guess the 'ice' part of dice sounds like an 's' which makes it sound like its plural.
I've always suspected that the confusion between dice/die (the gaming thing) and multiple die (a casting or similar) is why some people call multiple castings dice?