According to information found on social networks and the web dressing with pants under the buttocks would have began in the US prisons.
At the time, prisoners who wished to have a relationship with other prisoners needed to invent a signal that would not be recognized by the geol- ogers. Thus, by partially showing their buttocks, they indicate that they were available to be taken in by their comrades.
Here is one of the origins of what has become a fashion phenomenon.
