The bua in "my bua flares up" is, surprisingly, a native Korean word for an organ inside our bodies — the lungs. People of old called this organ that holds the breath drawn in through the nose bua, but it was gradually edged out by the Sino-Korean pye and the native heopa, both meaning "lungs," and today it is almost never used as an anatomical term. And yet — what happens when you grow angry? Your breath quickens, your chest heaves, and something feels as if it is swelling up inside. This bodily reaction was taken directly as the stirring of the lungs, the bua. So "bua arises" and "bua flares up" became phrases that carry over, exactly as felt, the bodily sensation of the lungs swelling with anger. It is a rare case where the name for a part of the body survived by shifting its meaning to the emotional reaction that very part displays.