Rubbish to the first answer. The phrase "going commando" dates back slightly more years than american the comedy Friends. It was first used in WW2, by recruits for the marines. As a test to their stamina, strength and boolshiness, recruits were made to run long distance in just there wool issue trousers. This became very painful and caused chaffing to the nether regions. Most dropped out half way through the runs, due to the discomfort caused. Those who made the distance were considered commando material, hence the saying.