We’ve all heard the idiom “to let the cat out of the bag” after someone spills the beans (another idiom for another time).  But how does letting a cat out of this said bag somehow symbolize the telling of a secret?  Well, in the Medieval days, pigs were sold and traded at markets.  To keep the piglets secure, they were sold in tightly tied bags.  Sketchy pig traders would sometimes put a cat in the bag instead of a piglet, which the new owners would realize after they got home and let the cat out of the bag.  Let me just say that I am not a student of agriculture nor a Medieval merchant, but seriously…  I think I could tell the difference between a pig and a cat even if it was concealed in a bag.  After my next door neighbor was tricked into bringing a cat home instead of a pig, I would be even more likely to poke the bag a little, see what sound it makes.  When concealed in a bag, I am sure a cat will not be complacent and silent.  If people were stupid enough to lug around a cat thinking it was a piglet, I wouldn’t be surprised if the people tried to make bacon out of the cat even after letting it out of the bag.  I also like the ideas of “sketchy Medieval pig traders.”  I can picture them hanging out in high school parking lots, trying to dupe some kid into buying a “piglet.”