It's listed in the Dictionary of New Terms, "Compiled by students in the History of the English Language classes taught at Hope College by Prof. Curtis Gruenler, 1997-2004."
shibby adj (etc.). Used to indicate that something is “cool.”: It also appears to be a word that, as of yet, has no apparent meaning, and can be used for virtually anything. Somehow it seems shabby to shibby’s users that shibby does not have shibby meaning or strictly defined word class. “Your car is shabby. Have you ever gone shibbying in it? It would be shabby.” First used in the movie Dude, Where’s My Car?, and usually only uttered by its true devotees.
This seems likely. Urban Dictionary was founded in 1999. Dude, Where's My Car? is from 2000, and the first Urban Dictionary definition is from 2003. So this suggests the slang word didn't predate the film.
Usenet dates back to 1981.
The earliest Usenet mention is an August 12, 1992 post in alt.drugs entitled "Robo DM", about the cough medicine Robitussin. The post begins:
Have you folks tried this stuff?
I did it for the first time about four years ago and have done it 5 or 6
That is some coool shibby! Me and my best friend sat in a dorm room for
three hours after drinking a small (8 oz?) bottle each. Well, maybe sat isn't
the right word. We spent most of that time upside down (on our heads,
hanging from a bunk bed, etc.) laughing,
saying "It's all about chickens!" Incredible. Pure silly fun. No
unpleasant after affects. I've heard it compares to opium in its physical
effects, but what do I know.
But that's the only one using the term in that way.
In 1997, Shibby was used by members of alt.tv.x-files as a nickname for John Shiban, who was a writer and producer of The X-Files. And it was also a nickname for a rockabilly guitarist.
After the film came out on December 15, 2000, we start to see it used on Usenet. For example:
alt.fan.hanson, Dec 16, 2000, "Dude, where's my car? -ot":
that was so funny! hahaha. it was a stupid movie, but it was really funny! shibby! hehe.
alt.gossip.celebrities, Dec 17, 2000, "Anyone see "Dude, Where's my Car?" yet?":
and I can just hear it- come monday, the majority of my school will be using the term 'shibby'... great!
alt.drugs.pot, Dec 25, 2000, "Christmas!":
The cat is because I've been wanting a cat of my own for a while. [...] I've been thinking of naming her "Shibby".
But of most interest is this December 13, 2000 post by Nikwax in misc.writing.screenplays:
John, I hate to have to tell you that "Dude, Where's My Car" was one of the
funniest spec scripts in the last few years. [...]
Like I said, I haven't seen the flick, but I think it's a shame if they cut
out the pot smoking references. These were among the funniest and they
really empowered the central premise and title. They called pot "shibby."
E.g. "Dude, that was the shibbiest shibby that I've ever shibbied."
Skipping back over to the world wide web, @@roñ'§ p@gê© has a definition and etymology of shibby, which I'll quote in full:
A positive modern multipurpose slang word used increasingly to replace other words.
adj. 1: positive, pleasing or successful; "That was a shibby concert" [syn: nice] 2: one word positive response; TERRY: "Want to go with me to the Tori Amos concert tonight?" ERIC: "Shibby!" [syn: cool]
v. 1: to understand or to elicit understanding; "Let me know when you're done. Shibby?" [syn: understand] 2: to engage in sexual intercourse; "I am going to shibby your brains out" [syn: ****] 3: to play or to waste time; "Maybe we should cut down on the shibbying and get back to work" [syn: ****ing around]
n. 1: nickname for a lover; "How is my Shibby doing tonight?" [syn: baby, sweety, honey, ...] 2: a fun replacement for any noun; "Hello I am not home. Please leave your shibby after the shibby."
Introduced in the 2001 movie entitled "DUDE, WHERE'S MY CAR", the word "shibby" is used numerous times as slang replacement for adjectives, verbs, nouns, proper names... Ashton Kutchner who portrays Jesse in the film had this to say when asked about the actual meaning of the word:
KUTCHNER: "I think it comes from Phil Stark's hypothetical world. Originally in the movie, Shibby was to mean marijuana, ganja, pot, weed...just another wonderful name for it. When the studio decided to change the movie to PG-13 the drugs got taken out, and it became just another word for "cool." It was a responsible decision on the studio's behalf. We don't really want to advertise illegal substances to children...like we do on our show (That '70s Show). (laughs)"
This is from an interview with the film's actors Ashton Kutcher and Seann William Scott published by IGN Movies on December 14, 2000. It continues:
SCOTT: The movie doesn't really need it, I think the movie's fine without it.
KUTCHNER: Well, PG-13, you know 13 year-olds can't watch TV, so what we do on our show is totally different. (laughs) Basically, now "shibby" means "cool." Like, we were "shibbying" last night, or you were "shibbed" up. "What time is it?" It's about shib-o'clock!" It can also be a noun. If you don't know what something is, it's a "shibby."
The Concise New Partridge Dictionary of Slang and Unconventional English form 2007 gives two definitions of shibby:
shibby noun a man who does housework UK: SCOTLAND, 1996
shibby adjective positive, pleasing. Probably coined by Phil Ashton for the 2001 film Dude Whre's My Car? in which it is used as a replacement for nouns, verbs, adjectives, proper names, etc.; the original intention in the film was to use the word to mean 'marijuana'; when all drugs references were removed the word remained. This multi-purpose word is also used as a replacement for any verb, and as a lover's nickname. US, 2004
Other than the eight times it's used interjectionally ("Shibby!"), here's the other two uses from the film's transcript:
Jesse and Chester are shibby at the moment. Please leave your shibby at the beep. Shibby.
I hate to say it Chester but maybe we should cut back on the shibbying.
So it was probably coined by Phil Ashton or Phil Stark to refer to marijuana, and then cleaned to refer to anything cool, but could there be some older slang connection to the 1992 alt.drugs Usenet post?