A Boston Globe article by Ben Zimmer traces the word “jazz” back to a Los Angeles Times story from 1912. It starts:
One hundred years ago, a hard-throwing but erratic minor league pitcher named Ben Henderson was getting ready for his opening day start for the Portland Beavers against the Los Angeles Angels. Henderson had pitched well for the Beavers the previous year, but he began the 1912 season with a well-earned reputation as an unreliable drunk.
Henderson gave a Los Angeles Times reporter a preview of what he had planned for the game. “I got a new curve this year,” he explained, “and I’m goin’ to pitch one or two of them tomorrow. I call it the Jazz ball because it wobbles and you simply can’t do anything with it.” The headline for the item, from April 2, 1912, was simply “Ben’s Jazz Curve.”
Ben goes on to describe how the term spread after that. A nice read in this spring training month.