Speculation: Joker's Real Name
With the coming of #Rebirth, Justice League #50 will reveal the Joker's name. (Previously thought to be Jack Napier when he disguised himself as a weatherman and Eric Border which he used when he disguised himself as an orderly at Arkham Asylum.)
The storyline has been hinted at Justice League #42.
Quote from Diana in Justice League #44. The page even starts with the Joker's face.
"There was one god my mother hated above all others. His name was Gelos. The God of Laughter. My mother didn't despise Gelos because Amazons don't believe in laughter. They do. It might not appear evident at times, but they believe in joy, happiness and love. Gelos did not. He followed my mother like a shadow across the battlefields. Laughing at those in pain. Jeering at men and women dying. He was invisible to us, but no matter where you stood, you could hear his cackling. It haunted her."
Gelos in Greek mythology, is the divine personification (god or daimon) of laughter. Believed to enter the retinue of Dionysus. Retinue means a group of advisors or assistants to an important person. Gelos basically hung out with Dionysus.
Other names related to Gelos is the latin name, Risus.
Dionysus is the son of Zeus and is the god of irrational and chaos. He appeals to emotion and instincts. His direct opposite is Apollo. In a way, Batman is Apollo while the Joker is Dionysus.
Joker was found to use "Dionysian/Dionesium" or was called the Dionysian Man (Batman #43?). Dionysian/Dionesium was named after the God, Dionysus.
Dionesium is a chemical compound that came from the blood of the Hyper-Adapter, who is/was a servant of Darkseid. Pure Dionesium gives anyone who comes into contact with it immortality. (Aw shit! Batman came into contact with him didn't he.)
The Hyper-Adapter, as fans have seen it when Batman was hopping through time, was designed by Darkseid to follow him through time and kill him. Eventually it got beaten and driven back through time to imbue Simon Hurt with a diluted Dionesium and ended up in died in the stone ages, where it got killed and skinned alive. Its corpse came into contact with Vandal Savage, who actually probably bathed in its blood which is pure Dionesium.
This same stupid Hyper-Adapter was given the name Barbatos by the dumb idiot, Simon Hurt. Barbatos soon became a term to refer to something or someone whose life was made immortal (or extended) by Dionesium
What we can gather is that Joker's name is Gelos... or Barbatos, the hole in things.
Or maybe... he just doesn't have a real name.
We won't be sure till they launch Rebirth. He is suppose to be someone whom we won't expect.
Other comic panels: