When I was first old enough to actually reach the showerhead in our bathroom, I discovered that you could rotate the outer ring fairly easily. Suddenly I found that the stream of water coming out was emitted from a different set of holes and in a more concentrated form. Turning the ring further intensified the stream and broke it up into a series of very fast pulses.
I wasn't aware of the notion of a showerhead massage yet so I called them bullets. It reminded me of those old Superman shows (this is pre-Christopher Reeve, mind you) where some gangster would pull out a Tommy gun and let loose on the man of steel. Superman would just stand there and let the bullets bounce off him. (A move that, in hindsight, is pretty obnoxious. "I could have that gun wrapped around your wrists before you even blink but I'll just wait while you do your sad attempt at machismo.")
I think Mom tried to explain to me the concept of why someone might want a massage, but I was a kid in suburbia and had pretty much zero concept of stress or tense muscles.
So when I had the time during a shower, I'd rotate the head around a bit, stand akimbo and pretend I was fighting a never-ending battle against a constant barrage of gunfire.
Took me years before I stopped calling it "bullets."