Cook someone’s goose

To upset or ruin someone’s chances of success, sometimes to kill. The expression dates from the early 19th century but its origin is unknown. It is, however, the subject of much folk etymology, such as geese being shown to medieval besiegers to indicate that the besieged town has plenty of food, only for the town and the geese to be burnt or cooked when the town was eventually sacked. Such stories are far from convincing, not least because of the many centuries between medieval stories like these and the appearance of the expression in the early 19th century.