This phrase, which literally means “to trick a demon into eating tofu”, refers to a feeble attempt at luring someone into an obvious trap. Oddly enough though, the phrase comes from a story of a wise scholar who was successful in doing just this.
Many years ago, a young scholar who was out on his travels decided to set up camp for the night. When night fell, a hungry demon happened by the camp, greedily licking his lips at the sight of the learned fellow. When the scholar noticed the demon eyeing him up, he had to think fast, knowing his life was in imminent danger. In a desperate attempt at self-preservation, the scholar called out to the demon, telling him that he had been traveling for days and was thus too smelly to eat. But, the young man told him, that while his own scholarly flesh wasn’t fit for demon consumption, he assured the apparition that there was plenty of delicious tofu left in his pot for him to enjoy. The ghost ate the tofu, leaving the scholar to live on and tell his tale.
Clever as the scholar was, we use this phrase in Cantonese to refer to a poorly thought out ruse. Perhaps it’s easier to trick a hungry demon than it is to trick a person.