To Be Boisterous, To Make A Fuss
Intransitive verb and Godan verb
さわぐ
騒ぐな！死にたいのか？死にたくなけりゃ黙ってろ。
Don’t make so much noise! Do you wanna be killed? If not, just shut up.
The kanji is boisterous. The verb version is to make noise or to be boisterous. Basically, you're being boisterous when you make a lot of noise, so that's where it comes from.
When you go to make noise and be boisterous, you go to the local 沢 (さわ) swamp. It's an awesome place, and people don't complain about the noise.