I believe the saying 'going commando' (without underwear)
was originally coined by American troops in Vietnam who had trouble maintaining clean underwear so went without.
Another school of thought suggests that the saying originated in the same place but for a different reason. It was the Yanks not wearing underwear because it was encouraging crotch rot when sweaty and dirty during long spells in the jungle.
I understand the term to mean going without underwear, as commandos do, because their battle dress has a flap at the back, as well as a zip at the front, which can be opened to allow for evacuation of bodiliy waste. Obviously wearing underwear would impede this operation, so they go without. The phrase passed into common usage when used in an episode of 'Friends' a few years ago.
Crotch rot, also known as gym itch, dhobie itch, jock itch and various other names is more properly known as Tinea Cruris. Hope that satisfies your need for correctness, Bluedolphin.