The 6-7 craze offered a brief window into the hidden world of children

In case you managed to miss it, 6-7 is a slang term - spoken aloud as "six seven" - accompanied by an arm gesture that mimics someone weighing something in their hands.

It has no real meaning, but it spawned countless videos across various platforms and infiltrated schools and homes across the globe. Shouts of "6-7" disrupted classrooms and rained down at sporting events. Think pieces proliferated.

For the most part, adults responded with mild annoyance and confusion.

But as media scholars who study children's culture, we didn't view the meme with bewilderment or exasperation. Instead, we thought back to our own childhoods on three different continents - and all the secret languages we spoke.

There was Pig Latin. The cool "S" doodled on countless worksheets and bathroom stalls. Forming an L-shape with our thumb and index finger to insult someone. Remixing the words of hand-clapping games from previous generations.

6-7 is only the latest example of these long-standing practices - and though the gesture might not mean much to adults, it says a lot about children's play, their social lives and their desire for power.

You can see this longing for power in classic play like spying on adults and in games like "king of the hill".

A typical school day involves a tight schedule of adult-directed activities; kids have little time or space for agency.

But during those in-between times when children are able to stealthily evade adult surveillance - on playgrounds, on the internet and even when stuck at home during the pandemic - children's culture can thrive. In these spaces, they can make the rules. They set the terms. And if it confuses adults, all the better.

As 6-7 went viral, teachers complained that random outbursts by their students were interrupting their lessons. Some started avoiding asking any kind of question that might result in an answer of 67. The trend migrated from schools to sports arenas and restaurants: In-N-Out Burger ended up banning the number 67 from their ticket ordering system.

The meaninglessness of 6-7 made it easy to create a sense of inclusion and exclusion - and to annoy adults, who strained to decipher hidden meanings. In the U.S., siblings and friends dressed as the numbers 6-7 for Halloween. And in Australia, it was rumoured that houses with 6-7 in their address were going for astronomical prices.

Since before World War I, historians have documented children's use of secret languages like "back slang," which happens when words are phonetically spoken backwards. And nonsense words and phrases have long proliferated in children's culture: Recent examples include "booyah", "skibidi" and "talk to the hand."

This 6-7 also coincides with a long history of children revising, adapting and remixing games and rhymes.

For example, in our three countries - the US, Australia and South Korea - we've encountered endless variations of the game of "tag". Sometimes the chasers pretend to be the dementors from Harry Potter. Other times the chasers have pretended to be the COVID-19 virus. Or we'll see them incorporate their immediate surroundings, like designating playground equipment as "home" or "safe".

Similar games can spread among children around the world. In South Korea, "Mugunghwa kkochi pieotseumnida" - which roughly translates to "The rose of Sharon has bloomed", a reference to South Korea's national flower - is similar to the game "Red Light, Green Light" in English-speaking countries. In the game "Hwang-ma!," South Korean children in the early aughts shouted the word and playfully struck a peer upon seeing a rare, gold-coloured car, a game similar to "Punch Buggy" and "Slug Bug" in the US and Australia.

Historically, children have reworked rhymes and clapping games to draw on popular culture of the day. "Georgie Best, Superstar," sung to the tune of "Jesus Christ Superstar," was a popular chant on U.K. playgrounds in the 1970s that celebrated the legendary soccer player George Best. And a variation of the clapping game "I went to a Chinese Restaurant" included the lyrics "My name is, Elvis Presley, girls are sexy, Sitting on the back seat, drinking Pepsi."

One reason 6-7 became so popular is the low barrier to entry: Saying "6-7" and doing the accompanying hand movement is easy to pick up and translate into different cultural contexts. The simplicity of the meme allowed young Korean children to repeat the phrase in English. And deaf children have participated by signing the meme.

Because the social worlds of children now exist across a range of online spaces, 6-7 has been able to seamlessly spread and evolve. On the gaming platform Roblox, for example, children can create avatars that resemble 6-7 and play games that feature the numbers.

The strange words, nonsensical games and creative play of your childhood might seem ridiculous today. But there's real value in these hidden worlds.

With or without access to the internet, children will continue to transform language and games to suit their needs - which, yes, includes getting under the skin of adults.

A great deal of attention is given to the omnipresence of digital technologies in children's lives, but we think it's worth taking a moment to appreciate the way children are using these technologies to innovate and connect in ways both creative and mundane.