whipping boy

noun2

1. •
   Someone punished for the errors of others.

   • In others he denounces it as rank Judaism, the Jew having at that time become for him the whipping boy for all modern humanity. — 1902
2. •
   (historical) A boy who was whipped in the stead of a misbehaving prince in early modern Europe.

   • As the whipping boy, he must take the whippings for the royal heir, Prince Brat.