During the Three Kingdoms period (220-280 AD), Cao Rui, the emperor of the Wei state, sought to recruit a truly capable official. He advised his ministers: 'When selecting talent, always beware of those with a false reputation. A false reputation is like a picture of a cake; it cannot relieve hunger.'
This idiom later evolved to describe the act of comforting oneself with unrealistic thoughts or illusions, without addressing practical problems.