Modern Slang vs. Traditional Idiom: `Fùhēi` can be seen as the modern, pop-culture equivalent of the classical idiom
笑里藏刀 (xiào lǐ cáng dāo) - “a dagger hidden behind a smile.” While the classic idiom is more formal and literary, `fùhēi` is the casual, everyday term used by younger generations, especially online.