Wenn man keine Ahnung hat, einfach mal die Fresse halten. If you have no idea, just shut your trap. The sentence is crude, and it is often quoted. It is attributed to the comedian Dieter Nuhr. He tried to register it as a trademark, but this failed at the Higher Regional Court of Stuttgart in January 2023. A similar line had already been spoken in 1974, in the WDR sitcom Ein Herz und eine Seele: Wenn man keine Ahnung hat, dann hält man bescheiden die Schnauze. If you have no idea, you modestly keep your mouth shut.