The origin of the term is contested, but may be derived from “George Stick”, named for a possible inventor.
I knew the device itself predated gaming, but I always assumed it gained the joystick name from some game company. I’m surprised to to learn its unrelated!
The more plausible explanation is that joystick comes from the aviation parlance and was originally ribald sexual innuendo (those flyboys did need to blow off steam), with the “George Stick” explanation being invented after the fact to come up with a plausible clean etymology.