SANTA ANA, Calif. — Parenting a "tween" has always been tricky.

They're on the cusp of adolescence, so it can be hard to understand the things they do ... and now, what they say can be just as mysterious.

To wit: "OMG, I was JK!"

Translation: "Oh my god, I was just kidding!"

Frances Biemann and her friends have been known to talk like this.

"We say 'IDK' — that's kind of like a word now, too," said Frances, a 12-year-old middle school student. (Stumped? IDK means "I don't know.")

She can't even pinpoint when it started.

"At first it was kind of weird, but now it just seems kind of normal," Frances said.

So what's with the alphabet soup, you ask?

Welcome to the age of acronyms. It dawned in the late 1990s as Internet users began flocking to message boards, and peaked a couple of years ago when everyone and their mother started sending text messages on their trusty little cell phones.

It has evolved into a spoken language among young teens and middle school students, who use acronyms to speak to their friends in shorthand, save a little time or tell off-color jokes in front of confused parents ("WTF" is usually involved ... take a guess what that stands for).

Some linguists and English enthusiasts have long rued the Internet's pernicious influence, but David Crystal has watched the acronym age with enthusiasm.

Crystal, a linguist who authored the Cambridge Encyclopedia of Language, said acronyms are nothing new.

The Roman and Hebrew cultures used them thousands of years ago. "SOS" dates to the days of Morse code, "ASAP" first appeared in the dictionary in 1955, and Crystal's own uncle said "TTFN" (ta-ta for now) when he went off to work in the 1940s.

As for today's acronyms, "some might end up with a permanent home in the language, but I doubt that most will," Crystal said. "It's too early to say. It feels like a fashion, which might disappear as quickly as it started."

Trend-watchers agree that acronyms are just that — a trend.

"A couple of years ago all the girls were more into the OMG talk," said Denise Restauri, founder of AllyKatzz.com, a social networking site for girls ages 10-15. "But as they get older and the years go by, they're doing less of it in general."

High school kids agree: They are so over the acronyms.

"We might say LOL sarcastically, if something isn't funny," said Nikki Ro, a high school senior. (For the curious, it means "laugh out loud.")

While high school kids still use acronyms when texting or chatting online, the novelty of spoken acronyms has faded, they say.

"If we use acronyms, we know that we're doing it," said Rosa Hong, a senior at University High. "We know it's going on, and we think it's funny."

What about those that use acronyms without irony?

"If they're being serious, they're freshmen," said Angela Lyonsjustus, a junior in high school. "They think they're being cool, but we don't take them seriously."

For now, the use of acronyms is still rampant among the precocious pre-adolescent set.

Many of today's middle school students started using the Internet in elementary school and have had their own cell phones for years.

The result: acronyms are part of their everyday vernacular.

And acronyms help Frances Biemann and her friends save time and multitask, she said. She can work on her homework while sending instant messages to friends and listening to music.

Acronyms have their place, Frances said, and she and her friends use them selectively.

"My mom doesn't really like it," she said. "She likes to know what we're talking about, so I kind of just use real words around her."