想像一下在熱鬧的市集攤位，一個小失誤就可能瞬間把生意搞砸。只要一個突如其來的動作，原本應該藏好的東西就被當眾曝光，眾人看得一清二楚。起源未經證實：這句話常被連繫到早年市集小販詐騙的傳聞（據說有賣家把袋子裡的豬仔偷換成貓）。
如今，to let the cat out of the bag 的意思是「洩露秘密」，多半是無意間或太早說出口。用在某人把原本應該保密的資訊不小心說溜嘴的情況。
應用
• 使用頻率：8/10
• 適用場合：Casual
例句
• I accidentally let the cat out of the bag and told Tom about the promotion before HR announced it.
(我不小心說溜嘴，把升職的事告訴湯姆，他還沒等人資正式公布就知道了。)
• We’re planning a surprise party for Sarah, so whatever you do, don’t let the cat out of the bag!
(我們要為莎拉辦驚喜派對，所以你千萬不要破梗喔！)
• I was trying to keep the surprise party a secret, but my little brother totally let the cat out of the bag when he asked Mom what she wanted for her birthday dinner.
(我本來想保密，偷偷幫媽媽辦驚喜派對，結果我弟弟去問媽媽生日晚餐想吃什麼，把整件事都給說溜嘴了。)
