v. To wear trousers without putting on underwear.
2001
Comedian Dave Gorman is also firmly with the traditionalists. 'I'm never ever naked beneath my trousers. If God had wanted men to 'go commando' he wouldn't have invented polycotton with two per cent lycra! When my zip broke once I was glad to have boxers on.'
1985 (earliest)
Furthermore, colored briefs are 'sleazy' and going without underwear ('going commando,' as they say on campus) is simply gross."
I read several reports that claimed this phrase came from Britain's Royal Marine Commandos who, one assumes, often go boxerless beneath their fatigues. I can't confirm that, but I do know that going commando hit the mainstream when it was used in a 1996 episode of the sitcom "Friends." I managed to find a couple of dozen citations since 1996, but I found only one before that.