Idol group that used to hide their names before debut

(1)BTS years
(2)When we were doing gym training
(3)J-Hope and I were changing in the dressing room
(4)Bangsan Year-end Group
(5)A member of 16 came and asked if you guys were going to debut
(6)4가 그렇다고 저희 곧 데뷔한다고
(7)New Year’s Party
(8)When I asked what the name of 14 would be
(9)Room 19 years
(10)proud of Jiyang’s horse
(11)It hasn’t been decided yet
(12)There’s someone who said it proudly here
(13)I didn’t tell Rap Monster’s relatives either
(14)She said, “I’m so proud that I’m confident
(15)Rap Monster was decided two years ago