BTS leader RM, who celebrates his birthday on Sunday, was originally known as Rap Monster.

The famed rapper from South Korea was the first one to be selected into the seven-member group and has led them since. Namjoon was originated with the stage name Rap Monster in 2017, 5 years after he had started his career.

RM released his first solo album, titled RM. His second mixtape, Mono was the highest-charting album by a Korean soloist on the Billboard 200 chart.

In a letter posted in BTS’ official fan cafe, he explained that RM seems more in accordance with the music’s he’s aiming to create and also provides a wider spectrum.

“I’ve been promoting under the name Rap Monster for about five years, since the end of 2012. It was a stage name that I naturally came to be called among our company family members and my members, after a line in a song I’d made as a trainee, and I think I became very fond of it. But once I started promoting, the name ‘BTS’s Rap Monster’ was a bit long, and I’ve become keenly aware of the fact that it’s become different from [what I want] to put at the front of the music I’ve made for the past five years, and the music I want to share in the future,” he wrote, as reported by Soompi.

At some point, I started introducing myself as Rapmon or RM, rather than the full name Rap Monster. So I’d like to change the name I use for promotions to ‘RM,’ which I think is more in accordance with the music I’m aiming for and also has a wider spectrum. Since I’ve already released some music and mixtapes as RM, I think that some fans will have already guessed this. I thought about this carefully for a long while, because I want to make music for a long time in the future with an unrestricted and open mind and view,” he added. 

“It’s possible that it’s a bit awkward to be changing my stage name, which I’ve been called since before my debut, and you may feel like it’s unfamiliar. However, I would be sincerely grateful if you would welcome me after I’ve started with a new name following a long time of consideration,” he concluded the letter.