I guess the naming also comes from the dimension you're looking at them. If you're constrained to one axis they're only positive and negative numbers. The other axis is the imaginary one because you can't possibly conceive it from your dimension. But if you have access to both dimensions there are no longer real or imaginary numbers but only complex ones. Quaternions. Hypercomplex numbers.

Like life, once you get out of a black and white understanding of your world, it's suddenly more complex...