Turns out, the difference between pity and intrigue is encapsulated by a goofy Germanic word that sounds like a stinky cheese. This past fall, a 13-year-old Brooklyn boy named Francisco Hernandez Jr. disappeared for 11 days, continuously riding the New York City subways back and forth undetected. This disturbing story was leavened somehow by the revelation that the boy has Asperger's syndrome. What could have been another urban-chaos statistic instead became cocktail-party fodder: Isn't it interesting?

Although the idea that a medical condition might be in vogue seems in poor taste, Asperger's is a malady for our times, just as ADD was considered symptomatic of the age of MTV quick-cut editing a generation ago. Any description of Asperger's, a form of functioning autism marked by social withdrawal or outburst-prone ineptness and, often, mastery of some arcane knowledge, has to set off cringes of recognition in anyone who considers even a phone call to be about the sixth most preferable form of social communication. LOL, amirite? The term also represents the Platonic ideal of self-aggrandizing slagging and conversational shorthand—it's exotic-seeming and highbrow in its specificity, but not so obscure as to confuse. (Plus, the word rolls off the tongue: Ass-perger.)

And with the news that Asperger's, which officially became a medical diagnosis only in 1994, might be absorbed into the autism spectrum by 2012, Aspies—don't flinch, Asperger's sufferers call themselves that—fear they stand to lose their means of self-identification. So before you rip into your girlfriend's affectless, sci-fi-geek coworker by throwing around the new A-word and feel pride for being an avid reader of the New York Times, remember a few things: (a) It is not a scarlet letter, (b) it may well be accurate, and (c) perhaps you should be jealous.

At least since Robert Benchley, an Algonquin Round Table mainstay, first used moron as a dig in a Vanity Fair essay (his demeaning phrase was "high-class moron," to be precise), the smart set has co-opted terms for psychological conditions in the name of building a better put-down. In wittier circles, getting a laugh at someone else's expense has become increasingly dependent on this sort of idiomatic specificity—it's not enough to make someone look dumb; we need to make ourselves sound smart in the process.

As terms that were once used clinically—idiot, cretin, spastic, and imbecile all used to have official diagnostic definitions—have been absorbed into the casual-insult vernacular, we've had to dig ever deeper to find one that can leave a mark. If Don Rickles were getting started today, he wouldn't be able to get onstage without a copy of the New England Journal of Medicine tucked under his arm.

"People are constantly seeking new sources of vocabulary, especially when it comes to ridiculing the awkward," says Ben Zimmer, a linguist and the executive producer of the Visual Thesaurus, a lexicology website. "We think of psychiatric terms as needing to be precise, but they fall in and out of fashion."

The reality of Asperger's syndrome can be summed up simply: "It's the inability to distinguish the conversation you're having with somebody from the one going on in your head," says John Elder Robison, who wrote the 2007 memoir Look Me in the Eye: My Life With Asperger's. Sound familiar?