Jax's name may derive from the Greek warrior Ajax.
The name may have also derived from Garet Jax, the legendary undefeatable weapons master in Terry Brook'sShannara book series.
Jax's background does not reveal where he came from before he joined the League.
Jax's outward appearance resembles the look of the "Garo ", a ninja-like tribe in "The Legend of Zelda: Majoras Mask".
In Jax's game information page on the beta version of leagueoflegends.com, his background image is an altered version of his classic artwork - altered to include a horned, shadowy figure. The shadow resembles Aatrox, although with enough differences that it could be another of the five darkin.
Skins
Vandal Jax does not appear to be related to the gang that has surfaced among the other champions with the vandal skins such as Twitch, Brand, Vladimir and Gragas. This is further supported by its release date, which preceded the other Vandal skins by a significant amount.
Vandal Jax may be a reference to Paragon Ash from playstation video game "Vandal Hearts" as the colour matches almost perfectly. An image of Paragon Ash can be seen here .
Jaximus is a reference to the Murmillo, a gladiator class from the Roman Imperial Age.
It might also be a reference to Maximus, the protagonist of the movie 'Gladiator', although Maximus wields a sword, rather than a polearm.
This skin features a memorial tribute to Joe, a Ewings Sarcoma patient who visited Riot thanks to the Make A Wish Foundation. Joe passed away on July 13, 2012. The movement quote for the Jaximus skin, Joe's favorite, was changed to "Here's to you, kid!" in his memory.
PAX Jax is a reference to the Cardboard Tube Samurai from the web comic Penny Arcade (which hosts the Penny Arcade Expo - PAX). A symbol on the skin resembles Pac-Man and matches symbols on the Samurai's gi and the shirt of Penny Arcade protagonist Gabe.
The Mighty Jax is a reference to 90's Disney Film The Mighty Ducks.