A "nooner", as far as the Urban Dictionary is concerned, is sex in the middle of the day. This is also the term used by Duck & Decanter to describe their sandwiches (says so right on the bag). Is this an implication that their food is as good as sex?
I have been here twice so far, and while I wouldn't equate their sandwiches with any kind of amorous activity, this is still and amazing place to order lunch. It's one of the few places in the Phoenix Valley that's comparable to the hof braus that I used to go to as a kid in San Francisco. This place is one where if it's lunchtime and I'm in the vicinity, eating there is a no-brainer. I will literally look for reasons to come here.
If I see you with a bag saying "A Nooner" on it, it either means that you are about to have a delicious meal, or you've just had one. Take your significant other here, and maybe you can have two Nooners together that day.