Rural people aren’t usually country bumpkins. In days past city slickers had to beware of buying a farmer’s pig in a poke, a pig brought to market in a bag, because the “pigs” inside such pokes were sometimes cats the canny country folk had substituted for suckling pigs. A merchant who bought a pig in a poke was stuck with it, but one who wisely opened the poke often let the cat out of the bag, revealing the crafty farmer’s secret. The deceptive practice was widespread enough in England for both expressions to be common well over four centuries ago. It may also have led to the expression left holding the bag, because anyone falling for the farmer’s ploy would be left with an empty bag on opening it, the cat inside darting away. This is only a guess, however; the empty bag could just as easily have been an empty purse held by a man robbed by his servant, and there are a dozen similar possibilities.