It seems "What for?" is BrE. And "For what?" AmE. But it may be that both expressions are interchangeable in BrE and AmE.
1 Answer
So what is your question? :)
I wouldn't say one is BrE and one is AmE. Usage depends on the context.
"Please jump up and down three times".
"What for?"
That could easily be heard in either country.
"I am going to make you pay".
"For what?"
Would also be common in both places.
You might occasionally use "What for?" in the second example, but I wouldn't expect anyone to say "For what?" in reponse to the first question. Either in Britain or America.
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And if you used What for? in the second example, it would mean something else: For what? would mean Pay for what?, and What for? would more probably mean Why would you do that?.– FærdMar 6, 2016 at 9:57
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"What for?" in the second case could mean either depending on your tone and how you emphasized the word "for". "What for?" could mean "why?", "What for?" would mean the same as "For what?" Mar 6, 2016 at 12:30