The word "soft" is often used in the sentence "pack up soft and run quickly" In ancient times, it usually meant that people who had committed a crime were afraid of being arrested by the government and had to pack up some important things. Gold, silver and copper coins are necessary, and you need to change clothes on the way to escape. So in the ancient story, those soft bags were full of gold and silver.
Warning fable: "light the lamp and pack all the soft bags with bottoms at home." ?