From Wu Jingzi's Qing-dynasty novel 《儒林外史》 (The Scholars), chapter 5: 次日早晨,大摇大摆出堂 — a magistrate strides pompously out to court. The image is of hips and shoulders swinging with theatrical self-satisfaction.
usage
Almost always pejorative — describes someone walking with too much display, either arrogantly or (like the thief) brazenly. Neutral 'walking confidently' is 昂首阔步.