"De Yu Wang Quan" comes from the "Zhuangzi: External Things" chapter. A quan is a bamboo fish trap. Literally, it means that after catching the fish, one forgets the trap. It is a metaphor for forgetting the means or foundation on which one relied for success after achieving one's goal. Its deeper meaning refers to a person who, after achieving success, proves ungrateful and betrays their original intentions, carrying a derogatory connotation. It is mostly used to criticize those who, after gaining fame and success, abandon old friends, forget their mentors, or deny their own roots. In terms of cultural background, Zhuangzi used it to expound the philosophy of "forgetting words once one has grasped the meaning," but later generations mostly adopted its negative sense, emphasizing gratitude and not forgetting one's original aspiration. In emotional coloring, it carries a tone of condemnation and regret, reminding people that even after success they should still remember the people and things that helped them, and must not burn bridges after crossing them.
📝 Example
When he first started his business, he relied entirely on his friends' financial support. Now that his company is listed, he forgets the trap once he has caught the fish, avoiding his old friends. (A metaphor for forgetting one's origins and betraying those who helped after achieving success.)
Some scholars, once they become famous, forget the trap once they have caught the fish, completely denying the research foundation of their early years. (A metaphor for forgetting the fundamental basis of one's success after achieving one's goal.)