This etymology was told to me a lifetime ago by my Shakespeare teacher in high school as an example of how words can change meaning over time, and I never forgot it.
The word shambles today primarily means a mess, a scene of disorder, something disorganized.
But it used to mean a meat market, or a butchery. In fact, in York, there's an area called The Shambles, where historically butchers plied their trade. It's a fascinating area, because of how the walls are close together to provide shade for the hanging meats, and how the street slopes down on both sides toward the middle, so as to sluice all the blood and offal more easily.
Anyway, the reason shambles became known as a butchery or slaughterhouse is because it refers to the bench on which the meats were laid out for customers to see. The word itself actually descends from some Old English, Old Norse, and Old Germanic words, ultimately derived from Latin scamillus, meaning a low stool or bench.
So the word really made a few twists and turns over the centuries. In English, the sense evolved from "footstool (1300s) to "place where meat is sold" to "slaughterhouse" (1540s), then figuratively "place of butchery" (1590s), and, generally, "confusion, mess" (1901, usually in plural).
