一鸣惊人yī míng jīng rén

What does 一鸣惊人 mean?

To lose something important because of carelessness, overconfidence, or ignoring warnings

指zhǐ因yīn为wèi粗cū心xīn大dà意yì、自zì信xìn过guò头tóu或huò不bù听tīng提tí醒xǐng，而ér失shī去qù重zhòng要yào的de人rén、地dì方fāng或huò机jī会huì。

Historical origin

During the Three Kingdoms period, Guan Yu focused on attacking Fancheng in the north and was so confident in Jingzhou's security that he repeatedly dismissed warnings about Wu's intentions and pulled defensive forces away from the river. Lu Meng of Wu disguised soldiers as merchants to slip past the river defenses, and because Guan Yu's own overconfidence had already weakened those defenses and left warnings unheeded, Wu forces were able to seize Jingzhou from within. The idiom centers on Guan Yu's culpable decisions: his dismissal of alerts and excessive self-assurance as the true cause of the city's fall.