Chips指(作賭注用的)圓形籌碼。The chips are down來自撲克牌桌，描繪的是下賭注的籌碼都已經(jīng)放在桌面上而打撲克的人即將攤牌一決輸贏的當(dāng)頭。這是最讓人提心吊膽的時(shí)刻，因?yàn)榻Y(jié)果未見分曉。后來人們把這個(gè)習(xí)慣用語廣泛地應(yīng)用在其它場合。

when you are in a very difficult or dangerous situation, especially one that makes you understand the true value of people or things

在困難時(shí)刻，在危急關(guān)頭

One day when the chips are down, you will know who your true friends are.

等到危急關(guān)頭你就會(huì)知道誰是真正的朋友了。