"It was quite a mad feeling. The gaffer came up with the nickname for me and then all the fans called me Billy. It took a while to adjust to. People would call me Billy and I didn't even know if they were speaking to me. I'd hear it when I was playing... I just hadn't really heard it before, so it was decent."
Anderson is part of the Newcastle United squad that has travelled to Austria this week as Eddie Howe intensifies his side's preparations for 2022/23. But the first half of the teenager's year was spent in League Two at Bristol Rovers, as former Magpie Barton's men sought a way out of the fourth tier.
"I loved it. I went there at the end of January and it was a new club to me," Anderson explains after training at United's base near Salzburg. "But they welcomed me so well and a lot of the lads were in the same boat, with a lot of them from up north, so I fitted in well and cracked on straight away.
"When I joined, there was a really good feeling around the place. They were pushing on. I don't think they had a decent start to the season, but as I joined they were pushing a bit and getting wins. From the very first week, we were pushing for play-offs, really, and then eventually pushing for automatic promotion. It was canny mad, really. We just went on a winning streak."
The Gas had been relegated from League One at the end of the previous campaign and sat 12th when Anderson moved to the Memorial Stadium. He grew to relish "that two-games-a-week physicality" and the "robustness" required at a level he often looked too good for. Barton, who spent four years as a player at St. James' Park, had designs on the play-offs but what happened next was remarkable.
"There were about six or seven teams who could either get in the play-offs or get into the automatic promotion places. It was so tight," says the Scotland Under-21 international, who registered eight goals - including his first ever senior strike - for Rovers. "We all had the same sort of aim, but with the type of group we were and the manager we had, we just pushed and drove everyone to the best standards we could.
"I think it was probably the best thing I could have done, to be honest. I thought I performed pretty well and I got goals, which was the main thing for me. I had good performances to start with and didn't get any, but it was one of my aims to get the goals and they finally started to come in. I got one and then I was like, 'right, now's the time'. They just started coming. Naturally I was in the right positions - I played higher up on the left wing after a few games, and I started getting into better positions from there."
The presence of Barton, in just his second venture into management, was keenly felt. "He was good. He had high standards for everyone. He pushed you. He was a player so he had your best interests in mind, and he really helped me and gave me that sort of stepping stone for my career. He told me a few stories about when he was here (at Newcastle United) and stuff that went on... it was a good laugh."
But for all the promise and poise exuded by Anderson in his four months with Rovers, it is his contribution on the final day of the season which will stand the test of time. He was a stand-out performer in the division - supporters had been calling him the 'Geordie Maradona' for some time - by the final game of his loan spell, at home to already-relegated Scunthorpe United.
Barton's side had hauled themselves from mid-table to within a whisker of the top three, winning 14 of their previous 24 games, but needed a thoroughly improbably swing to go up. They would need to better Northampton's result at Barrow, or win by five more goals than the Cobblers, to leapfrog them into League One. With five minutes left, Northampton were winning 3-1 - but, incredibly, Bristol Rovers were 6-0 up and needing just one more to win promotion.
"Quite a lot of people said we'd do it," recalls Anderson. "I remember someone saying they had a funny feeling we'd win by seven - I remember him saying it. I was thinking, 'I wish'.
"It was crazy. We had a left winger at left back, and right winger at right back, and then wingers in the winger spots so we just went all-out attack. It was quite a lot to do, really, but we believed in each other.
"At half time, in my head, I thought, 'it's a bit tough to do, that' - we had to score five more. But everyone kept trying, kept going. Chasing that final goal, we knew we just needed one more."
In the 85th minute, Antony Evans lifted up a cross towards the far post where Anderson was priming himself to leap. "I just thought, 'I have to hit the target - this is the last five minutes, I can't miss this'.
"I was just praying that it would come. I've jumped up at the back stick and got it in, and the stadium just erupted. I can't really remember what happened to be honest but I remember being on the floor, in the celebration, with fans all over."
The pitch invasion was immediate and Anderson was lost in it, embraced by Gasheads and Rovers folklore, and after a summer of recovery he is ready for his next hurdle. The Magpies' friendlies against 1860 Munich and Mainz in Austria may offer him an opportunity to show he has what is needed to become part of Howe's first team squad for the coming campaign. It is a chance he wants to make the most of.
"I've just got to try and impress as much as I can really, and do my best," he says. "I've got to try and compete for a place around the team and see how I can do.
"I think not trying too hard to do that (is important) - just do your stuff, and see if you catch an eye, and work as hard as you can. It's kind of like a free hit - I'll give it my best shot, and if they think I need another season out (on loan), I'm happy to do that. Whatever's best for me.
"I'd say for me, probably playing games is the most important thing, to be honest - carrying on my run that I have, and just trying to keep striving. Hopefully that's here, or if it's somewhere else on loan, I'll be giving it my all."
Whatever comes next, though, won't erase the memories of that Scunthorpe game in May. "It was a great day, for my family as well, and one I'll remember all my life," he nods. "Now I've got to push on for the next moment like that."
