The story
Judi Sheppard Missett created Jazzercise in Evanston, Illinois in 1969 after graduating from Northwestern University. After receiving a degree in theater and dance, she signed up to study with renowned jazz choreographer Gus Giordano at his Evanston studios. She was teaching at a dance studio and noticed her classes had high dropout rates. Realizing students were attending for physical fitness and not for performance, Shepard Missett began to hold "just for fun" classes that began with a jazz warmup. These classes, originally named "Jazz Dance for Fun and Fitness," were eventually renamed "Jazzercise."
From Wikipedia’s article on Jazzercise, shared under CC BY-SA 4.0.3