G-Dragon (A.K.A "GD") is trying to say
boomerang from mouth to mouth, I think he's using these words so he can make the others rhyme.
"Coup D'etat" is a word created by G-Dragon himself, it means Rebirth. He created this word because, when releasing this new album, he felt under pressure. So whenever he says the word he calms himself down.
In his music video, if you look closely and analyze the footage, you realize that he's telling a story. He explains it visually, so the message isn't very clear.
Click below to see what this entire song means, whether in English, Romanized or just regular Korean lyrics. Here: