The origins of the phrase “go commando” are uncertain, with some speculating that it may refer to being “out in the open” or “ready for action”.
Slate magazine’s Daniel Engber dates the modern usage to United States college campuses circa 1974, where it was perhaps associated with soldiers in the Vietnam War, who were reputed to go without underwear to “increase ventilation and reduce moisture”. However, more recently, Graeme Donald has pointed out that the US forces are “Rangers” rather than “Commandos”, and that in any case, the phrase was in use in the UK, referring mainly to women, from the late 1960s. The connection to the UK and women has been suggested to link to a World War II euphemism for prostitutes working in London’s West End, who were termed “Piccadilly Commandos”.
The term appeared in the 1982 novel Groundrush by Greg Barron, in the sentence, “Bigfoot’s jock snapped underneath, leaving him to ‘go commando’.” In the Chicago Tribune of January 22, 1985, Jim Spencer wrote, “Furthermore, coloured briefs are ‘sleazy’ and going without underwear (‘going commando’, as they say on campus) is simply gross.” The term gained currency in the popular vernacular after appearing in a 1996 episode of Friends.
In Chile, the act of not wearing underwear has been called “andar a lo gringo” (to go gringo-style) for decades.