This
database is a comprehensive collection of all the American idioms and slang available.
American Idioms are many and varied. We hope you enjoy our collection. We are adding more all the time.
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Don't let the cat out of the bag about Susan's Christmas present. At medieval markets, unscrupulous traders would display a pig for sale. However, the pig was always given to the customer in a bag, with strict instructions not to open the bag until they were some way away. The trader would hand the customer a bag containing something that wriggled, and it was only later that the buyer would find he'd been conned when he opened the bag to reveal that it contained a cat, not a pig. Therefore, "letting the cat out of the bag" revealed the secret of the con trick.