Green’s Dictionary of Slang

commando adv.

In phrases

go commando (v.) [? tough commandos need no such ‘soft’ apparel]

(US campus) to go without underwear.

1974		Eble Campus Sl. Apr. 1: go commando – to be without underwear.
1999		Roger’s Profanisaurus 3 in Viz 98 Oct. 15: go commando v. To freeball. To go out undercrackerless.
2005		Guardian 19 Aug. 3: There will be no more ‘going commando’ or melting boots for British soldiers [...] Regiments in Iraq and Afghanistan are being equipped with new kit, including ‘anti-microbial’ underpants.
2007		W. Ellis Crooked Little Vein 77: No way in hell was I going to attempt to get the underpants on. I’d go commando.
2012		Salon.com 5 Dec. 🌐 More actors are seen going commando and full-frontal: Is this a sign they’re relinquishing their masculinity?
2015		Florida Today (Cocoa, FL) 15 Feb. B6/2: The $9.7 billion toilet paper [...] brand [...] that dares consumers to ‘Go Commando’ after using it.
2021		S.A. Crosby Razorblade Tears 92: ‘Husband number three didn’t mind you going commando?’.