Happy Birthday, Thong!

It's time to honor the underwear that nearly brought down a presidency. It's the 20th anniversary of the thong.

When Frederick Mellinger began mass-marketing thong underwear — then known as "scanty panties" — back in August 1981, who knew it would become the fastest-growing segment of the multibillion-dollar women's under-apparel industry and a cultural phenomenon.

From Fifth Avenue to Kmart, ladies — and now gentlemen, too — can purchase these "unmentionables." The cheapies go for less than $15, while Calvin Klein or Tommy Hilfiger can ask for $200 or more for theirs.

White House Thong Moment

The thong — a skimpy panty in front and a thin strap in the back — was just a novelty item back in 1981, something sold alongside crotchless and edible undies. But now we all know about "That thong th thong thong thong," as Sisqo sings.

The infamous Bill Clinton-Monica Lewinsky White House affair began with a steamy thong moment, according to Independent Counsel Kenneth Starr's report. "In the course of flirting with [President Clinton]," the report states, "[Lewinsky] raised her jacket in the back and showed him the straps of her thong underwear."

Sure, they can be sexy. But many women say they've embraced the thong, sometimes known as "butt floss," in the never-ending quest to hide those visible panty lines. There is, of course, the "wedgie" factor. But what's a little discomfort in the name of looking good?

There's no doubt the everyday woman has embraced the thong. While only the daring don the thong in its beachwear form, as underwear, it has found its way into millions of women's wardrobes. Thong sales have more than doubled since 1997, while sales of regular panties have grown only about 10 percent, according to one fashion research group.

"These days, a woman comes into Frederick's of Hollywood and she buys maybe one corset. But she'll buy six, seven, eight thongs," says Frederick's spokeswoman-model Lee Ann Tweeden. "I can't even tell you the last time I wore full-bottom panties, and I think a lot of women who work everyday jobs in offices would say the same thing."

Tweeden, 28, has been modeling Frederick's undergarments for 10 years, "more than a lifetime in my business."

She says it doesn't matter what size or age a woman might be — thongs are for everyone.

"It used to be scandalous," she says. "Now it's a necessity. Clothing is form-fitting, and nobody wants lines."

From Loincloths to Silk and Hemp

In the early 1980s, thongs represented less than 5 percent of Frederick's sales. Now, the lingerie giant sells more than 75,000 a week. That accounts for more than 90 percent of sales. Over the years, Frederick's has developed more than 100 different colors, styles and fabrics, from low-rise to the "Rio," from cotton to charmeuse.

And there's plenty of competition from specialty houses. At online retailer Stephanna's Curves, full-figured women can find titanic teddies, and yes, thongs to fit a size 22 rear end. The proprieters say that "sex appeal does not come in a size 2 package."

If you're the crunchy-Granola hippie type, there's the all-natural, eco-friendly hemp thong. "You'd be surprised how well they sell," says George Bates of Shirt Magic in Lewiston, Calif.

"This is for the woman who has one eye on the environment and the other eye on impressing her boyfriend."

Of course, the thong existed long before Mellinger revolutionized the underwear industry by mass-marketing it. Some folks would trace its history all the way back to the cavewoman's first loincloth.

But the more conservative historians point to the 1939 World's Fair in New York City, when Mayor Fiorello LaGuardia decreed that the city's nude dancers cover up a bit. Thus, the G-string was born. And the G-string begot the thong.

Six years later, the orbit of the Earth was brought to an abrupt halt when French designer Louis Reard unveiled the bikini at a Paris fashion show. It was named after the Bikini Atoll of the Marshall Islands, where some of the first atomic bombs were tested, and since then, it's had a similar effect on men.

The Bikini That Started It All

But it wasn't until 1974 that fashion legend Rudi Gernrich married the thong bottom to the bikini top. Gernrich was the man who pioneered unisex fashions. In the disco era, he unveiled clothing that made a woman look nude under the flashing lights of a dance club.

Only the most daring of women took to the beaches in a Gernrich original. But Mellinger, who roamed the world looking for "the next big thing" to introduce to Americans, saw that it was popular in Brazil.

In a stroke of genius, he decided the thong had a future not only as a bikini, but as underwear. Some women may have thought it was sleazy — but not for long.

"I have 10 years of thong experience under my belt," says Lisa Concepcion Giassa, 30, a faithful thong wearer from Bogota, N.J. "One thing I know about, is the thong lifestyle."

Back in 1992, when the original Jurassic Park hit the screen, and her husband was just a college boyfriend at Rutgers University, Giassa caught her first suntan in a thong at a local park.

"The park was totally empty and I felt comfortable in my thong undies," she said.

"Well since my booty was never in the sun before I got sunburned on my butt. I came home and my husband [then boyfriend] saw what I did to myself and said, 'instead of Jurassic Park, I'm going to call you Your Ass Is Dark.'"

This story has a happy ending. She got a new nickname, and the couple married six years later. Now, every time "I go to the Jersey Shore sporting my thong bikini, my hubby reminds me to put the SPF on my bottom," she says.

But when it comes to wearing tight skirts and pants, the thong should not be taken lightly. "It's one of the best inventions of the 20th century," Giassa says. "I'd rank it up there with the invention as the ATM machine. Very convenient — and no lines!"

As a thong model, Tweeden says she's happy if she's contributed to the underwear revolution. "My family is proud of what I do," she says. "It's modeling in Frederick's. It's not Hustler."

But what about thongs for men? "I've seen them on guys," she says. "But not willingly … I just want to shout out, 'Get a towel, cover up, please!'"

Buck Wolf is entertainment producer at ABCNEWS.com. The Wolf Files is published Tuesdays and Thursdays. If you want to receive weekly notice when a new column is published, join the e-mail list.