Amixem is the online name of French YouTuber Maxime Chabroud, known for gaming, comedy and group videos that built a huge French speaking audience on YouTube. Short isolated lines from creators like him often get clipped and shared as reaction sounds, and this oh ta gueule moment spread in that way across edits and soundboards. The phrase is everyday French slang for telling someone to shut up, so even viewers who do not follow his channel understand the joke instantly and reuse it as a quick conversational stop.