I would think that a internet search would answer all your questions. From my limited knowledge of the subject. Gunpowder was invented by the Chinese around 1400 we now call that Black Powder and use it for various things but mostly in muzzle loading firearms. It is a powder and is graded by how course the powder is from ffff to f and even canon powder. I have made it, it is simple to make requiring only 3 ingredients Salt peter, sulfur and charcoal. If I remember correctly it is 75% Salt Peter, 10% sulfur and 15% charcoal. So Gun powder has always been called powder. Now when they invented smokeless powder which is not a powder but pellets or balls, we sometimes call them kernels, they never changed the name because it was intended for the same purpose as a propelent for a cartridge.
It is like "almond milk" It is not milk because all milk comes from a mamual. But to market it and get you to buy it as a substitute for "milk" they call it almond milk. I have yet to see someone milk a almond but you get the point.