www.alphadictionary.com

To give someone what for

(To scold or punish)

This curious idiom seems to have arisen in something like the following way:

Parent: I'm going to punish you.
Child: What for?
Parent (furiously): What for? I'll give you "what for"! You know what for!

"I'll give you...." is itself an idiom, meaning "How dare you say....". Somehow the expression "I'll give you what for" then came to refer not to the punisher's fury at the querying of the punishment, but to the punishment itself. It's strange how phrases develop.

Interesting. Any ideas on when it entered the language?

It seems to have originated sometime during the 19th century. The Oxford English Dictionary dates its earliest known use to 1873. Wiktionary's earliest citation is from 1912.

Do you find that this phrase is now used in a more preemptive fashion? Meaning, the speaker is not reacting to a "What for?", but simply saying, "I'm going to give/show you what for!"

In your example, we would get rid of the rest of the dialogue and stick with just a first sentence, as in the above.

A furious statement, that doesn't require any prelude.

Yes, I agree. We don't put what for in quotes any more. Grammatically, it's just a noun phrase which defies word-by-word analysis.

Grammatically, it's just a noun phrase which defies word-by-word analysis.

Would that perhaps be the definition of an idiom?

Would that perhaps be the definition of an idiom?

I would define an idiom as a phrase whose meaning is not apparent from the definitions of its individual words. Most idioms, however, obey the rules of grammar, e.g. "in the nick of time", "on tenterhooks", "down and out", "on the spur of the moment". A few, however, such as "what for" and "by and large", are impossible to analyse grammatically.

The earliest uses of "what for" to mean some sort of abuse that I can find are

1888 "Colonel Quaritch, V.C." by H. Rider Haggard: "If I don't make Boisingham, yes, and all England, too hot to hold you, my mother never christened me and my name ain't George. I'll give you what for, my cuckoo, that I will!"

1890 "The Drums of the Fore and Aft" (a short story in Indian Tales) by Rudyard Kipling: "'Now,' gasped Jakin, 'I'll give you what-for.' He proceeded to pound the man's features while Lew stamped on the outlying portions of his anatomy."

Note Kipling's use of the hyphen to make it one lexical item.

In the first ten years of the 20th century the phrase seemed quite popular. Jack London for one used it often.