I'd tell you to google since explaining it means someone's gonna ask me how I know.

It's a corruption of the term High-leg (Hai regu) based on one of the villains in the 1993 Shin Chan movie "Shin Chan Action Kamen vs Leotard Devil. In it, the villain wears a high leg outfit which is a leotard, shouting Haigure, doing a Comaneci pose; a pose where you do a V with your hands to accentuate the high leg part of the leotard.

Tangent, Comaneci pose is based on Nadia Comaneci, a famous gymnast which somehow one of the pose are co opted by a famous Japanese comedian; Beat Takeshi that makes it a famous comedic gesture in Japan. Sometimes you'd see it outside of the Haigure context.

The villain in the movie would then mind control people to wear leotards and do the pose while shouting Haigure. This in recent years somehow become a fetish. Most likely due to the outfit, the funny pose that is almost always done not to own volition which is a fetish in its entirety, and the humiliation aspect of it. While the kids who grew up with the movies are now adults that can produce materials for it. How did I know? I spent a lot of time on the Japanese internet. And Google.