In medieval England, long before refrigeration, butchers slaughtered only as many animals as they could sell in a day. Guts, offal, and blood were tossed into an open-air gutter (called a runnel), that was generally running down the middle of the street.
All the stuff they chucked out–unsold meat, as well as the inedible bits and pieces of slaughtered animals–were called “shambles.” Hard to imagine what it must have smelled like at the end of a hot summer day.
Nowadays, the word “shambles” means a state of complete disorganization.