머리가 돌다.

The phrase '머리가 돌다' (meoriga dol-da) is a combination of '머리' (meori), meaning 'head', and '돌다' (dol-da), meaning 'to turn' or 'to spin'. Literally, it translates to 'one's head is spinning'. This imagery directly conveys the idea of confusion, disorientation, and a loss of mental stability. When someone's head is spinning, they can't think straight, they might feel dizzy, and their perceptions can become distorted, all of which are associated with irrational behavior or losing one's mind. This idiom is a vivid and common way in Korean to describe a state of mental derangement or extreme frustration that leads to irrational actions. It highlights the head as the center of thought and reason, and its 'spinning' as a malfunction of that center.