den Kopf zumachen

Verb

 * 1) to stop worrying, to recess
 * 2)  to shut up,
 * 1)  to shut up,

Usage notes
Either sense seems limited in milieus, not reliably understood by every German. The sense of shutting up is traced to soldiers in the 1930s and GDR youth language in the late 1970s, and in the 2010s it is commonly encountered in the Ruhr Area whereas unused in.