Fooling about the other day, as you do, I told someone I'd give them what for, meaning that I'll swipe them one.
I'm not sure I heard it correctly back then, so is this turn of phrase generally known?
Where does it come from?
I wonder if it might pertain to a person getting whacked and then saying 'Oww, what for?!'.

Or possibly...

"Go to your room"

"What for?"

"I'll give you "what for". Now GO!!"

NOT speaking from experience

That use of "what for" is part of the vernacular in Michigan. And I like Doc's surmise of its origination.

I agree Sparteye. Our medic of snugness seems to have found a likely origin. Strangely enough, I don't think I've ever heard it used exactly as described.

Echoing doc_c and Sparteye, I have heard the expression from my youth from my Scotland born Chicago raised father and used exactly as doc_c described.

I heard it in New England also. Parent: "Go to bed now, or I'll give you what for." (without child having said a word.)

Parent: Wash the dishes.
Child: What for?
Parent: "Wash 'em, or I'll givya what for!

I've also heard it commonly used in a sporting context: Go out there and show 'em 'what for'!

Scout leader: Run and get the potfer, or I'll give you what for!

Scout: Potfer? What's a potfer?

Scout leader: to cook in.