Or, at least, I was hope you do, cuz I haven't a clue.
In
Birds of Prey, Huntress has used this phrase twice when talking to a man. The first time is in
#57. Helena has just caught a kidnapper, has him hanging upside down and is interrogating him.
The second time is in the newest issue,
#84. She's talking to Dick (Nightwing), a friend and ally of hers, and remarks that she didn't think of him as the type of guy who carries his wallet in his front pocket.
At Gail Simone's forum, she's been asked point blank what it means several times, and she just teases us, though she did say it isn't a small penis joke, and implied that it's a slang term girls use about guys. This means I'm supposed to know it. I am, however at a disadvangage as I have no close female friends, and those I do have don't tend to talk about guys. The guys at my comic book group have no clue.
So I'm going back over to the convention now, and I expect an answer when I reemerge
Which might not be for eight or ten hours.