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".
[6] However, more recently, Graeme Donald has pointed out that the US Forces refer to "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.
[1] 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"