Posted by Bruce Kahl on November 06, 1999
In Reply to: Let the cat out of the bag posted by bluebaron on November 05, 1999
: Have also heard that this applies to dropping/weighing anchor on sailing ships.
I am not 100% on this but at medieval markets, unscrupulous traders
would display a pig for sale.However,the pig was always given to
the customer in a bag containing something that wiggled, 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.