We have, I assume, been speculating. And despite our best efforts, we were unable to come up with a meaningful purpose for this little pocket.
A mobile phone, little banknotes, or other items cannot be kept there since there is insufficient space for them. the keys, too? You’ve got to be joking; getting the key is not feasible for you.

But fear not—the British tabloid The Independent claims to have the solution to the age-old riddle, and it’s probably not what you’d expect.
You might have given it some thought now and then. All jeans, whether they are for men or women, typically have two front and two rear pockets.
One of the front pockets occasionally has a little pocket as well. Why, though, is it there?

It’s fascinating since we have to go back almost 200 years to pinpoint the origin. That little thumbnail-sized pocket was more of a functional solution to a problem that no longer existed than a stylish addition to pants.
The brilliant concept was created by the well-known Levi’s jeans firm.