After years of dancing around giving the Joker any truly definitive origin, a recent comic in an ongoing series has casually dropped said origin on fans, along with the original Joker's name. The importance of comic book origins has always been major for their characters, but the Joker's is a truly special case.

The Joker is one of the rare characters who doesn't really exist well on their own, but rather as a foil for another specific character, namely Batman. With how terrifying he is in just about every aspect, Joker never really needed a backstory to work, as knowing more would just lessen the terror.
This is why the Joker's backstory has remained vague and nebulous, with multiple possibilities for who he truly is. According to the Joker himself in The Killing Joke, one of the most important Joker stories ever penned, he likes to keep his backstory as "multiple choice." The latest issue of Flashpoint Beyond may well have put all that to rest though, as the name of the Joker, rival to one of DC's most manipulative heroes, has been confirmed to be Jack Oswald White.

That's certainly a name, and its origins come from a few places. Jack was the name of Joker's original identity in Tim Burton's Batman, and has been used for other incarnations of the character throughout the years. To be clear, this particular story deals with multiple realities (or Earths), and so there are multiple Jokers. This one, however, is specifically stated to be the one from Earth-0, the original reality of the DC universe, and the originals of all their heroes. Thus, despite some brilliant retcons to DC's continuity involving the Joker, this latest one seems to place him firmly as one man named Jack.
As for the actual backstory of Jack Oswald White, it falls pretty neatly into what many have considered a high probability of his origins. Jack was a failed comedian who the world dealt one too many hard knocks to, eventually driving him mad. It's not too far removed from the 2019 Joker film, and with Joker 2 getting a release date, it's an origin that will become more prominent. Ultimately, this information will probably not change who the Joker is in most stories too much, which is probably a good thing. Joker is often at his strongest when directly opposed to Batman, which is why Joker not appearing in Gotham Knights is probably for the best.

Source from gamerant.com by Mason Sansonia