I never heard this expression until recently. Apparently it's used down south and basically means "pardon me" or "excuse me." To you southerners, is this saying used where you live?
Well, if southern Ohio is considered the south, then yes. It's pretty common. A variation is "say what?" We also say "please?" in the same context.
ha, interesting saying i grew up saying "what's doin'?' that means: how ya doing? - or did...not many say it anymore haha
haha, i've lived in the south for most of my life and the only time i've really heard this expression used was when i watched an "old" episode of Aqua Teen Hunger Force on Cartoon Network - Frylock was trying to tell Meatwad to do something, and Meatwad kept saying "do what now?" over and over since the big CN is based out of Atlanta, i'm sure they picked up the inspiration from somewhere local, just like they did when they dreamed up the Squidbillies
"do what now?" is an expression to indicate that you don't understand what it is you are being told to do, or else you understand and just think it's a bad idea, or you were not fully paying attention to your instructions. this differs from an expression meaning "pardon me" or "excuse me." at least that's what it means around here. "do what" minus the "now" is, like i mentioned already, not used in this area.
Don't mock us when most of you guys can't even say vehicle with out breaking it down in to 1234567 syllables.