Their name is short for "ABSOLUTE SIX", meaning that the full line-up of BRANDNEWBOYS achieve absolute perfection when the five members and the fandom are together. Their name is also an abbreviation of "ABOVE BRANDNEW SIX" which reflects the hopes that the five members and their fans will open up new horizons for Brand New Music.
Youngmin, Donghyun, Woojin and Daehwi were contestants on Mnet's boy group survival show Produce 101 Season 2. Woojin and Daehwi finished in 6th and 3rd place, respectively, thus debuting in the project group Wanna One. Youngmin and Donghyun were eliminated and finished in 15th and 28th place, respectively.