Origin

This character combines water on the left with a sound hint on the right. The water component makes sense because the main meaning involves liquids boiling or bubbling up. The right part, pronounced roughly like "futsu," is a sound hint that tells you how to say the word but doesn't add to the meaning itself. Together, the character visually suggests the idea of water doing something active and energetic — which matches the bubbling, fermenting, and turbulent senses of the word.