Britain's Got Talent: Where did KSI get his name - what does it mean? YouTuber wows BGT fans with guest judge spot

YouTuber and influencer KSI joined the show as a guest judge, filling in for former Strictly judge Bruno Tonioli. Fans have already warmed to the internet personality on the show, with ITV bosses reportedly lining up a deal to sign him onto the show on full-time basis after pulling in millions of viewers.

KSI, whose real name is Olajide "JJ" Olatunji, is best known to the younger generation who have grown up watching the star on YouTube. He began making videos on the site in 2009 and quickly gained popularity for his comedy gaming videos, which mostly focused on FIFA.

What does KSI stand for?

KSI stands for ‘Knowledge, Strength, Integrity’. JJ got the name from a Halo clan - a community of gamers who play the popular video game Halo.

His first YouTube channel was launched under the name “JideJunior” in 2008. He switched to using KSIOlajideBT on his channel, which has since been rebranded as JJ Olatinji, although he is still referred to as ‘KSI’ in professional settings.

After gaining popularity on YouTube, he also launched a career in music and in boxing, as well as promoting the energy drink Prime alongside his former boxing opponent and fellow influencer Logan Paul.

The star joined Britain's Got Talent for the show’s 18th series. Before his guest debut, which viewers saw on last week’s premiere episode, JJ said: “It was so fun. I just wanted to get as involved as possible and really immerse myself into the space and just enjoy it.

“And I thoroughly did, the auditions were incredible. There were some incredible singers… who just blew everyone away in front of that audience, it’s just incredible.”

He added: “I watched the likes of Susan Boyle and Diversity, so for me, being a guest judge was mind-blowing. And then what really hit me was when I saw my name at the top and just the big X. I was like, oh my god. I’m actually here. What the hell? Like this is ridiculous.”

Britain’s Got Talent continues at 7pm on ITV1, STV, ITVX and STV Player on Saturday, March 1.