Origin of "Slush Fund"

"Slush" is an old word for used fat or grease. During the 19 century sailors would scrape out all the old fat and grease that had been used to cook the endless meals of salted pork that they were fed when the pease pudding had run out, and sell the used fat to people on the port who didn't know where this came from. The cash from this dodgy business would go into a kitty and be used to buy food and especially alcohol for the whole crew. From all this comes the idea that a "slush fund" contains money siphoned off to finance illicit enterprises.