Why is there a small pocket in the trouser pocket?

Jeans were originally designed for pocket watches.

In the past, the pocket watch was the main timekeeping tool. When you take off your clothes in hot weather, there is no place to put your pocket watch. You can put it in this small pocket. This small pocket can hold coins and receipts, so don't worry about dropping or losing them. Now this small pocket is rarely used to hold things, but more used as a decoration on pants. Jeans, also known as tweed pants, are work clothes worn by early pioneers (cowboys) in the western United States.

Generally, it is made of yarn-dyed denim blended with pure cotton and cotton fiber as a kind of casual pants for men and women. Thick blue jeans are reinforced with copper rivets at the tension point, and the trouser legs are tightly wrapped around them. The front pants are seamless, the back pants are seamless, the door is equipped with a zipper, and the left and right sides of the front pants are equipped with oblique pockets. The back piece has two pointed waist patch pocket, and the seam of the bag mouth is nailed with metal rivets and decorated with open thread.

Jeans were originally invented:

Speaking of jeans, people naturally think of 1849 gold rush in America. At that time, the first immigrants who set foot on the American mainland were poor and had to work hard. Strenuous labor makes clothes wear easily, especially in 1849, when miners flocked to California, which formed the famous gold rush at that time. Because cloth breaks easily, people are eager to have a durable dress.

At this time, some factories use Genoa canvas to produce work pants, so they call that canvas Genoa canvas, which means "Genoese". Later, pants made of that canvas were simply called Genoese pants and evolved into jeans as durable as jeans. Levi's, a Jew, is recognized as the inventor of jeans.