Origin

[CASpeight]

Where does 'going commando' come from

[j2buttonsw]

Try this for starters: http://new.theanswerbank.co.uk/Home.go?category_id
=&search_text=commando

[Quizmonster]

Click http://www.wordspy.com/words/gocommando.asp for a possible answer.

[JohnPPotts]

I find it hard to believe this has a real basis in the military as people who spend days in the wild would appreciate the value of multiple layers, including thermal underwear. Wearing the same underwear for days on end seems far more likely (though apologies to any military types who see this answer as an insult to their machismo!)