This is the term they use in prison when someone gets hanged.
There were many hangings in Berlin, in which
the victims would twitch and jump at the end of a rope...hence, doing the "Spandau Ballet." Also, there were
frequent suicides of Nazis being held for trial at the Spandau prison. A hanged person tends to
jerk around and "dance" if the death is caused by strangulation (and not a snap) they say. As the years went by it progressed to floorless dance or waltz or the air rumba.