When we talk about jeans, we usually talk about ‘five-pocket jeans.’
On the front, you have two curved inset pockets with pocket bags usually made from unbleached twill—although the pocket bags on the earliest jeans were sometimes made from of the same fabric as the rest of the pant.
Then you’ve got a small pocket that’s half-tucked into the left front pocket. It’s known as the coin pocket, the watch pocket, or the match pocket.
And lastly, you have two stitched-on and pointed back pockets.
Actually, jeans originally had only four pockets. It’s a common misunderstanding that the coin pocket is the fifth pocket. In was, in fact, the left back pocket that was added last.
The pockets on jeans were designed to be sturdy and easy to access. Back pockets were originally placed further out on the hips than they are today. And they’re pointed is to make it easier to reach what’s in them.
Over the years, the purpose of especially the back pockets has changed from a matter of practicality to how they shape the body of the wearer.