My grandpa told me about the screwball when I was about 8. He was a pitcher in the old Texas League. He was right handed. In the old days, left handed pitchers first threw the screw ball and it was called a screw ball for a very good reason. Back then there were no real power tools. To screw in a screw, and mostly into old growth hardwood in those days, the left hander turning the screwdriver inward developed a strong twist that direction. Right handers turned it the opposite direction. Picking up a baseball and throwing it the same way you turned screws was a natural motion for left handers.

True story. Came from a guy who pitched to Babe Ruth during exhibition games.

I didn’t know why it was called a screwball, but I suspected that it might be because it took a “screwball” to throw it. Based on the following, it appears I was on the right track.

http://www.hardballtimes.com/main/printarticle/what-a-screwball/

According to the article, Rob “Neyer argues that the screwball has been largely supplanted by the split-finger fastball and the circle change-up….” So apparently you’re correct in your assessment that “The circle change is a version of the screwball.”

Must be what Leach throws, because his change definitely fades away from righthanded hitters. So does the change that Stults throws, but not, at least in my observations, nearly as much as Leach’s change.

Know why it is called a screw ball?