To some within the Yankees, it was just a tweaked slider. Some viewed it as a sweeping slider. At one point, the organization dubbed it a “whirly,” acknowledging it was a new offering altogether.

The new pitch — which is not really a new pitch — has officially made its way into the major league lexicon and has gone mainstream as a sweeper.

This season, MLB’s Statcast has taken a cult pitch and introduced it to the wider baseball world, now showing up on scoreboards, stat websites and TV broadcasts with its own distinct classification.

Last season, the Yankees’ Clay Holmes threw two different forms of breaking pitches, one with more horizontal movement (the sweeper) and one with more depth (the slider). He has not changed his arsenal this year, but according to the pitch logs, he now has a new offering.

The Yankees were early adopters of the pitch in their development ranks, so let’s ask them: What exactly is the sweeper?

“I think of it like I’m throwing a sideways curveball,” said reliever Greg Weissert, who has thrown 38.4 percent sweepers this season.

Imagine the plunge of a curveball, but executed horizontally rather than vertically. A sweeper is a breaking pitch that darts sideways more than a typical slider and seems — thanks to the ball’s seams, but more on that later — to rise simply because it does not fall very much. The very best sweepers, such as Shohei Ohtani’s, can travel 20 inches from right to left for a right-handed pitcher.

“The biggest thing is it just doesn’t move like you anticipate the ball moving a lot of times,” Yankees pitching coach Matt Blake said. “It just has more horizontal [movement], but it doesn’t go down as much as you expect it to. It usually stays above the barrel.”

Blake first learned about the pitch when he was a pitching coordinator with Cleveland, where Corey Kluber used the sweeper to win a pair of Cy Young Awards in the mid-2010s. Trevor Bauer picked up the weapon from his rotation-mate. Mike Clevinger began trying it out, too, and it began spreading within the organization.

Cleveland wasn’t alone, though. The forward-thinking Dodgers and Astros also discovered and taught the revelation. Others had happened upon the pitch independently, including longtime reliever Adam Ottavino, a native of Brooklyn who grew up watching David Cone, Orlando “El Duque” Hernandez and Jeff Nelson frustrate hitters with knee-buckling breaking balls.

Ottavino picked up his version of the sweeper and paired it with a more traditional slider, then reached the majors in the early 2010s and found the sweeper worked better.

“It’s a really big, horizontal-breaking slider,” said Ottavino, now in a sweepers-heavy Mets bullpen with Jimmy Yacabonis and Brooks Raley. “I didn’t invent it, but I did probably feature it more than anybody in ’14, ’15, ’16, ’17.”

The pitch’s nastiness was evident before its physics.

The Yankees began teaching it to complement arsenals of pitchers with two-seam fastballs, using a similar grip that plays with the seams.

“I don’t think there was much information around why it worked that way or how guys were doing it — just Kluber did it, and then guys kind of replicated off that,” Blake said. “And then here [with the Yankees], we started to learn more about it just in terms of the seam orientation and some of the spin effects from where the seams are lined up.”

High-speed cameras have changed the game and turned an art into more of a science. Observable forces at play when a baseball is thrown traditionally were known to include gravity, which forces the ball downward, and what is known as the Magnus Effect, in which, for example, a pitch with backspin fights gravity and stays up longer, while a pitch with topspin embraces gravity and dives.

In recent years, the proliferation of technology has permitted another phenomenon to be studied. Dr. Barton Smith, a professor at Utah State University, has published studies on what has been coined “seam-shifted wake,” which is more about axis and less about spin frequency. The notion entails that the seams of the ball also interact with the air and play with its direction. A sweeper (or two-seamer) thrown correctly can use the seams to fight gravity.

“We’re looking at it from one lens,” Blake said, the “we” including Yankees assistant pitching coach and pitch-designer Desi Druschel and senior director of pitching Sam Briend. “Barton Smith was looking at it from a different lens, more of a physics lens. And then we were just seeing it from watching guys pitch, and then there was this kind of qualitative look at some of the more objective information.”

The Yankees have thrown the fourth-most sweepers in all of baseball this season, and their minor league system is filled with practitioners of the pitch. Nestor Cortes, Schmidt, Holmes, Weissert, Michael King and Wandy Peralta throw the pitch that science might not have created but did help define.

The sweeper works best against like-sided batters — a righty pitcher wants it to dance away from a righty batter. According to Schmidt, who throws his version at an average of 86.6 mph, in between a slower curveball and a faster cutter and two-seamer, the key is in its velocity. The movement will be there, but a slower version will be easier to pick up.

“I’ve had a lot of success with mine because I’m throwing it pretty hard, and it’s got eight to nine inches of horizontal [movement], which is on the upper end,” said Schmidt, whose sweepers have held hitters to a .250 average this season.

As a whole, the pitch has been more effective than most. Major league hitters are batting .202 against sweepers this season with a .364 slugging percentage. Against all other pitches, batters are hitting .247 and slugging .404.

But the secret is out, and it has a name. The more sweepers hitters see, the better they will adjust.

The organizations on the cutting edge no longer have an advantage they had a few years ago, when only a few pitchers had a weapon that kept moving sideways and kept fighting gravity.

“Just like anything, the more you see that pitch, the less unpredictable it is,” Blake said. “People just start to train their eyes to it.”

So what’s the next sweeper?

“Good question,” Blake said. “I think we’re still looking at that.”

— Additional reporting by Mike Puma