An expression of solidarity between supporters and players, the iconic slow chant — accompanied by a single clap in unison — has been adopted by fans of teams including China, India, Thailand, Lebanon and Iran.
India captain Sunil Chhetri led his team of unlikely Vikings in a lusty thunderclap after the Blue Tigers thrashed Thailand 4-1 in Abu Dhabi.
Chinese fans followed suit after their team’s 2-1 win over Kyrgyzstan, and it has gathered pace since.
“Nobody does it like we do of course — but it’s really cool that more countries are using it to support their team,” Hilmar Jokull, vice chairman of Iceland’s noisy Tolfan supporters group, told AFP.
“We’re just a tiny country in the middle of nowhere and we’re not expecting anyone to copy us — especially countries of more than a billion people.
“The Viking clap gets the players pumped up,” he added. “It gives them an adrenalin shock.”
Iceland, with a modest population of just 340,000, famously reached the quarter-finals of Euro 2016, knocking out England along the way.
Their passionate fans also won admirers around the world, although — whisper it — the thunderclap actually originated in Scotland, and supporters of Icelandic side Stjarnan pinched it after a Europa League game in 2014.
“They took it from Motherwell, but I think it’s similar to the technique Vikings used when they were sailing,” insisted Jokull.
“Banging a drum to keep the rhythm going while they were rowing.”
Wales and France also celebrated victories at Euro 2016 with impromptu versions of the Icelandic chant, which gradually gathers speed and ends with a throaty cry of “Huh!”
For Iceland supporters, particularly Tolfan’s “ultra”-style fans, the thunderclap is a serious business, expressing the Icelandic concept of “samheldni” — which combines elements of unity and cohesion.
“All your muscles go tense,” explained Jokull.
“The sense of communion and togetherness between the team and the fans is amazing.”
Chinese fan Lin Dewei said his fellow supporters had adopted the thunderclap to “show the players love”.
“To tell them ‘jiayo!’ (fight) and also to say thank you for wearing the red shirt of China,” he added.
Thai fan David Prasong thought the thunderclap came from the Queen song “We Will Rock You” — until corrected.
“Embarrassing,” he grinned. “But it feels great to be part of it.”
While some fans at the Asian Cup may not be familiar with the chant’s origins, they make up for it with enthusiasm.
“I watched Euro 2016 and Iceland’s fans looked like they were having great fun,” said Lin. “That’s what it’s about really.”