第三教 · Dai Sankyo
Kata Guruma 肩車
Shoulder Wheel
Mechanic
Tori drops low, pulls uke's arm so their body folds across tori's shoulders, draped like a load in a fireman's carry, then stands and wheels uke across the shoulders, rolling them off the far side to the mat.
Analogy
A farmer squats, hoists a huge sack of grain across the shoulders, and carries it balanced behind the neck. At the wagon, one heave, and the sack rolls end over end across the shoulders and tumbles off the far side.
Why it maps
The shoulders are the axle in both: a long load draped across them is lifted from one side and wheeled over to drop off the other, which is exactly what 'shoulder wheel' means.