rock-scissors-paper => 가위 바위 보 (가위=scissors, 바위=rock, 보=paper) 보 is actually short for 보자기, a piece of flimsy piece of flimsy cloth used to collect and wrap things(http://tinyurl.com/ybbe2w7z). So it's similar to paper in this game. "If you don't do it you lose, rock-paper-scissors!" => 안 하면 지는 거야. 가위 바위 보! / 안 하는 사람이 지는 거야. 가위 바위 보! => 아무것도 안 내면 지기. (Whoever fails to show their hand loses, okay?) 내다 = show one's hand. -기 in 지기(from 지다: lose) is a special sentence ending used to assert rules for games, commonly used among children. - 자, 도망치기 없기 => Okay, we won't allow running away. - 한번 둔 수는 무르기 없기 => No taking back a move already made.

It's 가위바위보 가위 scissors 바위 rock 보 paper They just say "가위바위보" by shaking their hand 3 times and then they show paper, rock or scissors. I don't know for the "if you don't do it you lose" part