Or Should That Be, “Whddya Know?!?”
“What do you know?!” might very well be the Swiss Army knife of expressions.
I count no fewer than five different meanings:
#1. What do you know about something nefarious; accusatory.
Police to burglary suspect: “a Rolex watch is missing from the hotel room; what do you know [about it]?”
#2. “I’ll be [dam*ned]!” (sometimes preceded by “Well!,” and substituting “whaddya” for “what do you”). Often uttered to one’s self, in a disbelieving or stunned tone:
News headline: “Kim Kardashian just won the Nobel prize for literature.”
Reader: “Well, whaddya know?!?”
#3. Disqualifying, usually deployed when someone is losing an argument badly. Often uttered defiantly or disparagingly, with “you” emphasized:
Parent: “High school dropouts seldom find jobs that pay more than $1 million a year.”
Child: “What do you know??” But see, “Kim Kardashian” (or should be that be “butt?”).
#4. Greeting.
Uttered enthusiastically (and declaratively, vs. inquisitively); popular amongst Baby Boomer (or older) men.
“What do you know!!” See also, “How’s it going?” and “How’s tricks?”
#5. Evaluative; literal.
Job interviewer to job candidate: “What do you know [about fill in the blank]?”
Example: “What do you know about transductive quantum mechanics?” (sound impressive? I made that up 🙂 ).
See also, “The Many Guises of ‘Hot Dog’“; and “Which “Done” Did They Mean??”