“I am so not XYZ”

I have no idea about the usage history, but I will say that that article is *so* off-base. I will agree that "so" is never formally used that way, and I'll ignore the arrogance that oozes from that article. That aside, one of the adjectival meanings of “so” is “to a great extent”. Try replacing it with the similar adjective “truly”; it sounds perfectly proper now, huh?

As for your final example: “I am unprepared for this meeting.” Is equivalent to “I am not prepared for this meeting.”
“I am so not prepared for this meeting.” infers that not only are you not prepared, but you’re expecting to crash and burn. :)

My idea is to look to movie scripts...I want to say it began as early as the 90s with this movie I can't remember the name of, but she was, like, blonde--or even during the "Vally Girl" days of Moon Unit Zappa.

I would say the origins come from California. Now, if we look at the culture from there, there are conclusions we can draw. Look at the word, "dude," now, the expression "so not doing ___." Do we actually think a New Yorker would create the need to use this sort of syntax?

I *so* don't want to sound like an idiot if I am wrong, but my hunch is that it comes from the skateboarder/surfer/snowboarder lingo. This would be my first hunch.

Hey! I have this Cultural Antrhopology extra credit assignment to do, let me give you the link...maybe we all can find the answer there?

http://cfprod01.imt.uwm.edu/Dept/FLL/linguistics/dialect/index.html

My other tip would to be to ask a linguistic anthropologist from Harvard...I feel that they must be doing research like that.

Hmmn...

Yes, it seems to be a valley girl expression. I think we--in this string of comments--all understand what it means. As to the question where it came from, I'd like to add that it seems to be a play on words that changes parts of speech. In order to use the "I am so xyz" construction, you need an adjective. I am so pissed, etc. So wouldn't it be fun, the valley girls must have thought, to make other things adjectival. He is so Graham Norton, etc. Taking a noun and unexpectedly turning into an adjective in this way is wordplay similar to taking a noun and making it a verb: "He got punked."

Why can't "so" be an adverb? "He is so xyz." "He is truly xyz." "So" has a number of adverbial meanings.

Ingas - You make a valid point, altho I don't think I said otherwise. I was addressing the adjectival use of a noun. But since you mention it, I do believe that "so" is a type of adjective. I don't think it can be used alone as an adjective. It can be alone in a transition, like when I say, so, that is my conclusion. This usage is equal to the word "therefore."

But if I use "so" to describe something, I use it to describe the extent, as in "so beautiful". In this usage, it is, I would say, an adjectival modifier. It modifies the adjective that modifies the noun. It answers the question "Okay, it's beautiful, but how beautiful is it?" Even when you say "Yes, it is just so," you are simply indicating that the situation that had been described needs no further modification. The situation description itself is an adjective to the noun--in this case, the situation being described. "Just so" in an answer to that desription modifies the extent of the adjective by expressing the opinion that no further modification is needed.

When "so" is used to describe an extent it is an adverbial usage. And it is often used alone as an adjective. http://dictionary.reference.com/search?q=so

I agree with everything stated in the article. It's incredibly annoying to hear people misuse the word "so" so often (so not unoften?). How does it "ooze arrogance"? It does a perfectly rational job of illustrating this pervasive societal problem. It's not just kids speaking this way. I actually hear GROWN ADULTS, co-workers no less, talking this way.. "I am so going home now" ... "that is so not fair" etc. Not only that, I actually see people WRITING that way! You hear it in TV commercials and shows, which implies that somebody actually wrote that way ON A SCRIPT! Why on earth would anybody WANT to talk or write that way, much less actually do it? Do they even realize how awkward and immature they sound? Another thing that annoys me is when people draw out the word "so" with multiple o's in written text... e.g. "I am soooooo happy.." Why not draw out all the other words too? "I ammmmm soooooooo happyyyyyyy??" See how stupid that looks? Idiots.

You don't like the way it sounds (even thou it does appear to be perfectly grammatical) therefore anyone how uses it is an idiot -- nice.

Language is alive no matter what that article may wish.

The major flaw in your argument is that the construction "does appear to be perfectly grammatical". In fact, it does NOT appear that way. It doesn't even appear "grammatical" (much less "perfectly" grammatical). "So not prepared"??? It appears awkward, cumbersome, and silly to an educated eye and ear. It reminds me of an argument I once had about the word "data" and how the word should be used (singular or plural). The word is obviously the plural of "datum" and should be treated as such. For example, "these data are no good" as opposed to "this data is no good". The person with whom I was arguing kept insisting that the "this data is..." construct sounded more correct. My response was basically that it only sounds "correct" if you're ignorant and have no concept of singluar vs. plural. Hey, to many imbeciles, "that ain't no good" sounds perfectly acceptable. That, however, doesn't necessarily make it correct..

::sigh::
so
adv.
3. To a great extent; to such an evident degree

Usage defines a language, not written rules. And data is widely accepted as a collective noun.
(I'll refrain from using scare quotes.)

Oh, come on now.
look at these:
I am happy.
I am so happy.
I am unhappy.
I am so unhappy.
I am not happy.
I am so not happy.
Clearly, ...so not.... is very awkward, but just as clearly, grammatically correct. Why, that's the very point. That's exactly why it's funny, isn't it?
I would have to guess that the TV show, Friends is either the originator, or at least the force that popularized this particular twist of language.