In the days of sail, the water cask was called the scuttlebutt. Here the sailors would exchange rumors hence the name scuttlebutt for rumors. Today the drinking fountain is called the scuttlebutt but it is still the place for rumors. Now the poop deck was officers country. Officers were believed to know what was going on, they had the skinny. So the real information came from the poop deck. Over the years the poop deck was shortened to poop. Hence the poop is the true story. RW