Neck riddle

The neck riddle is a riddle where the riddler (typically a hero in a folk tale) gains something with the help of a non-solvable riddle: saves his life, wins a hand of a princess, etc. The name comes from the folk tales of type "Out-riddling the judge" (Aarne–Thompson classification system for folk tales #927), when the hero saves his neck by out-riddling the judge.