第二教 · Dai Nikyo
Kosoto Gari 小外刈
Minor Outer Reap
Mechanic
Tori clips uke's heel from the outside just as uke commits weight to it, pushing uke's upper body backward at the same moment. The support foot shoots forward and uke sits down hard onto their back.
Analogy
The cartoon classic: your heel lands on a banana peel and shoots forward ahead of you. Your foot goes where it was headed, just far too fast, and the rest of you drops straight back onto the ground.
Why it maps
The peel carries the weight-bearing heel forward out from under you exactly as the reap does, leaving nothing under your center and dropping you flat on your back.