Toy guns have existed basically as long as guns have. I’ll blow your mind by further pointing out that so have toy swords and toy bows and arrows.
All of us grew up with cap guns as kids. Or suction cup dart guns, or airsoft guns, or those little plastic disk shooter guns, or battery powered M16’s with a little light bulb in the muzzle that went rat-a-tat-tat-tat through a tinny little speaker when you held down the trigger. When I was a kid, one friend of mine had a battery powered minigun like Arnold had in the Predator movie, and in addition to mock gunfire noises it would spin all the barrels and it had a motorized knocker in it that simulated recoil. For an eight year old kid, it was the best thing ever short if something that fired an actual projectile.