IDIOMS

go commando

(idiomatic, intransitive) To forgo wearing underpants.

Example: 1996, Friends (TV series), "The One Where No One's Ready" [3.02], Act 2, approx. 12 minutes (of 23):
  Ross: … why do you have to wear underwear tonight?
  Joey: It's a rented tux, 'kay? I'm not gonna go commando in another man's fatigues.