Let us begin by defining "slang." According to Webster, it is "the specialized vocabulary and idioms as of criminals and tramps, the purpose of which was to disguise from outsiders the meaning of what was said."

With that in mind, let us move on to slang's current poster child, "junk."

Yes, junk -- as in what one traveler famously warned airport security people not to touch, as in what Brett Favre is alleged to have texted, as in what's "in the trunk" of women with voluptuous derrieres.

If these references make you feel like an outsider, well, consider counting your blessings. But for those who know that junk is a euphemism for male genitals and, to a lesser extent, female posteriors, the question remains: Why do they call it junk?

After all, Webster also says that junk is "useless or worthless stuff." Name one man who would make that connection.

So we contacted Grant Barrett, a lexicographer in San Diego and editor of the "The Official Dictionary of Unofficial English." He also is a vice president of the American Dialect Society, an academic group devoted to the study of English in North America since 1889. In 2004, he wrote a definition for "junk" in "The Double-Tongued Dictionary," for words "from the fringes of English."

It turns out that the origins of "junk" are murky, "so, as expected 'junk equals genitals' doesn't yield a lot of concrete answers," Barrett said. "It's easy to speculate, but impossible to prove any number of theories." Still, the study of language often leads down some fascinating byways, so let's look at the theories.

Barrett said that the earliest reference for junk as a body part appears to be 1986, when a writer named Ethan Mordden used the term in a story called "Buddies," in which one character threatened to drag another "outside and kick your junk in."

While the context isn't perfectly clear, Mordden's fiction often involved gay culture, which lends the term some credibility, according to Barrett. "Much slang does first appear as part of the language of a small in-group, such as homosexuals, and then, through accidents of history or quirks of social dynamics, manages to survive, spread and even thrive," he said.

Still, almost a decade passed before there was another concrete reference, on a discussion board about wrestling. By the turn of the century (or millennium; read into that what you will) the term was catching on. "Junk" began popping up in blog posts, song lyrics, magazine articles, even Craigslist. It made network TV dialog, in "How I Met Your Mother," in "Parks and Recreation."

Barrett stopped paying close attention around mid-decade, but suspects he could find "zillions more uses of the word since." As for "junk in the trunk," Barrett could find no evidence to show that one reference is connected to the other.

In the final analysis, he said that junk is a euphemism in the same way that "package" or "basket" refers to that particular male body part: "It's kind of a 'placeholder' name."

But probably not for much longer. The airport encounter with TSA officials became a viral video, which has spawned a spate of pitiable songs posted to YouTube, a line of T-shirts and sweatshirts emblazoned with "Don't Touch My Junk," and endless punch lines from mainstream comics such as Jay Leno: "Have you heard the TSA's new slogan? We handle more junk than eBay."

And that's how a bit of slang starts to die.

Kim Ode • 612-673-7185