text: Frigg, a Norse goddess, asked everything in the nine worlds not to kill her son, Balder, who was doomed to a tragic death.  But she neglected to ask the mistletoe, because she thought it so harmless.  Loki tricked Hodr into killing his brother, Balder, by throwing a branch of mistletoe through his body.  *  I couldn't find where it says how it became a kissing tradition.  But I heard it somewhere before, and it was something like: Frigg thought it should never again be used for something so terrible, so everyone should hang it over their heads and kiss under it.