[2] 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" (that is, avoids being sentenced to a death by hanging) after outwitting a judge with riddles.
and Óðinn's final riddles to Vafþrúðnir in the Old Norse poem Vafþrúðnismál and to King Heiðrekr in the Gátur Gestumblinda in Heiðreks saga ("What did Óðinn whisper in Baldr's ear before Baldr was cremated?").
The answers cannot be decipherable to the audience because if they could be figured out, the narrative movement would be destroyed.
[...] The neck-saving story commonly involves a confrontation with death by the protagonist.
The story turns on how to convert Death into Life; and the theme of the riddles in nearly all cases turns on descriptions of oblique situations in which Life emerges phoenix-like from Death.