Going commando....

Driving down 575 today, I hear a sentence come from my 3 year old's mouth that I was not expecting, and thankfully I didn't run off the road!! She was sitting in the back, and all of a sudden I hear, "Mommy, do you remember the time I was at Courtney's house and I was going commando?" I didn't really know how to respond, but I just started laughing!!!!! She hasn't been to Courtney's house since May, and even so, how does she know what going commando means?????