I would like to understand the history of the modern expression “what say we” followed immediately by a verb phrase, used to make a suggestion and common in informal speech, as attested at Oxford Dictionaries
What say we take a break?
used in publication
“Gillette Raises Bar With Five Blade Razor”. What Say We Make It An Even Dozen.
(Businessweek headline)
and found in song lyrics
Baby, what say we stay together? (George Strait song “What Say”)
What say we go and crash your car? (Brand New song “Failure By Design”)
I stopped to notice that this expression is not, strictly speaking, grammatical and seems to be a contraction. I became curious what it might be a contraction of. There is the slightly longer “whaddya say we [suggestion (verb phrase)]” which is an informal version of “what do you say we”. This is still not, strictly speaking, grammatical. But it seems akin to “what say you to [suggestion (noun phrase)]”, such as the Shakespeare quotation offered in comment by AndrewLeach
What say you to a Neats foote?
which can equally be expressed as
What do (or would) you say to a Neats foote?
But I have no idea if it is reasonable to connect the dots.
Best Answer
The two earliest instances I can find for OP's exact sense are...
It's probably relevant to note that both cases involve a significantly "non-standard" speaker.
As noted, the "What say you?" dating back to Shakespeare isn't precisely the same usage, because it refers back to a question or issue previously raised (effectively, "What say you to that?"), whereas OP's usage refers forward to a suggestion about to be raised by the rest of the sentence.
I think it's particularly a characteristic of informal/careless/uneducated speech to discard quite a lot of words if they contribute little to the sense of an utterance (either because they're highly predictable, or because they're only there for the sake of grammaticality. The less well-educated hostess might be more likely to say "Cuppa?" where Lady Muck says "Would you like a cup of tea?"
Here's an earlier instance of an expanded form in Jack London's 1903 Novels and Social Writings...
I see the modern usage as just a contracted form of "What do you say to the proposal that we...?" which doesn't actually adhere to any grammatical rules at all. By contrast, "What say you?" was perfectly grammatical in Shakespeare's day (before do-support rose to prominence, and we started replacing constructions like "Know you him?" with "Do you know him?").