In the Vietnam War, soldiers often went without underwear to increase ventilation and reduce moisture. The phrase was popularized in the 1996 episode of Friends: ‘The One Where No One’s Ready’. Otherwise known as the most notoriously low budget episode of Friends ever. They just all get bloody changed in two rooms the whole time.
The Chilean version of ‘going commando’ is ‘Andar a lo gringo’. Which means that our stereotype in Chile is that we don’t wear pants. As far as stereotypes go, it’s not too bad.