Defining what a witch is, is not all that easy. Probably the closest I can get is someone who performs a kind of magic. Not magic like pulling a rabbit out of a hat. Magic like working with energy or power that we don’t understand.
Way back when the planet was inhabited by folks living in small tribes and scratching out an existence most people didn’t understand what was going on around them.
Why did lighting suddenly flash from the sky? How come it got cold part of the year and hot the other part? Why did that one kid die while all the others lived?
People are curious. We want to know why. We want to know what is on the other side of the horizon. We tend to do things we shouldn’t trying to figure this out.
It takes time to look into and hopefully understand things. That was why the elders where considered to be the wisest in the tribe. The people doing all the hunting and gathering usually didn’t have time to look into the unknown things. This tended to be the forte of the eccentric folks. The man or woman that lived out away from the others. The old lady with a dozen cats or that guy that ran around talking to himself all the time. These kinds of people found themselves driven to look into the questions other simply ignored.