얼쑤 (eolssu) is a traditional Korean interjection called a chuimsae (추임새). It doesn't have a direct one-to-one translation, but it's used like shouting "Hooray!", "Alright!", or "Let's go!" to express excitement and encourage performers, especially in traditional music like pansori.
In "IDOL", BTS proudly blends these traditional sounds into a modern K-pop track. Using 얼쑤 is a powerful statement celebrating their Korean heritage, perfectly matching the song's core message of unapologetic self-love and pride.
IDOL is basically BTS telling critics to mind their own business while having the absolute time of their lives. Right from the start, they tackle the debate over labels: "You can call me artist, you can call me idol". They do not care which box you put them in because "I'm proud of it / 난 자유롭네" (I'm free). People can point fingers, but the group brushes off the gossip with the blunt Korean comeback "넌 너나 잘하셔" (you just mind your own business). They mix global pop swagger with traditional Korean culture, tossing in folk celebration chants like "얼쑤 좋다" (olssu jota - roughly, 'cheers, that's great!') and "덩기덕 쿵더러러" (dung-gi-duk kung-durureo), which mimics the beat of a traditional Korean drum.
The lyrics bounce between comic book heroes and Hollywood directors. One line drops "Face off 마치 오우삼" (Face off like John Woo), referencing John Woo's classic action film Face/Off where characters literally swap faces. That ties into their idea of identity: they might play the superhero "Anpanman" (a beloved anime hero with a bean-bun head) or balance "몇십 몇백 명의 내가 있어" (dozens, hundreds of versions of me inside). Yet instead of stressing over who they are supposed to be, they shout the main rule of the track: "You can't stop me lovin' myself". It is noisy, confident, and completely refuse to apologize for taking up space.