Why do they call it "commando" when a person doesn't wear underwear?

My guess is that military dudes “sans briefs” in a hot sweaty jungle started it.

Here is an article that affirms SeventhSense’s guess: Do Commandos Go Commando?

Maybe it has a link to the phrase “going balls out”.

It’s suggested that it derives from an earlier Scottish term: “Going Regimental”, because we all know that Scotsmen don’t wear anything under their kilts.

Because the troops are ready for action when out of the barracks.

I am not sure why they call it that, but I am willing to bet that it became more common to call it that after it showed up in a “Friends” episode.

It was really TMI for me when Jesse Ventura (who was a Navy Seal) confirmed this when an interviewer asked him about it.

I really didn’t need that image burned into my retinas for life :)

And Gordon Ramsey also confessed to the same due to working in the extreme heat of a professional kitchen. But at least he’s easy on the eyes (even tho his volatile personality is sine qua non in the obnoxious category)