cough up- give, come up with, produce: "Cough up the dough" = "Give me the money" Pay the piper comes from the legend of the Pied Piper of Hamlin. A travelling (pied) piper (a person who plays the pipe- a musical instrument) arrived at a village that was suffering from the bubonic plague, a disease spread by rats. He said he would lead of the rats out of the village by playing a special song and drown them in the river if the village paid him. The mayor offered him a large amount of money, and so he killed all of the rats, but then the village refused to pay him. So he played another special song and all of the children followed him out of the village. So it means that you must do what you promised to do or there will be bad consequences.