Northeron is the name of a location where some of the Wildhammer dwarves lived. Some of the dwarves in the Second War came from Northeron. Northeron was known for its mysterious ironwood tree forests, the torrential storms from its frozen mountains, ominous and foreboding peaks, and jagged ice cliffs. It is said that a gryphon aviary was hewn from solid rock by the dwarves of Northeron. The feral dwarves of the Northeron wildlands offered the service of their Gryphon Riders to assist in the decimation of the foul orcs who had desecrated their homeland and slain the leader of the Alliance forces, Lothar, in Blackrock Spire assault. Chief Thane Kurdran Wildhammer of Northeron was the most famous of these Gryphon Riders.
It appears to be a separate realm from that of the Aerie Peaks region as both locations are mentioned in Day of the Dragon. It also appears to have nothing to do with Northrend which is mentioned separately in the book.
CataclysmThis section concerns content exclusive to Cataclysm.
In early sketches of Azeroth, Northeron appeared to be within Quel'Thalas, north of eastern Lordaeron (Eastern Plaguelands) and north of where the Hinterlands are located. It is still possible that Northeron may be a subzone within the Aerie Peaks or the Hinterlands, but it may be the unfinished zone north of the plaguelands. Northeron may be short for northern Lordaeron, but the term Northeron predates World of Warcraft.
It is possibly simply an older or different name for the Hinterlands (Tides of Darkness, published after the creation of the Hinterlands in WoW retroactively confirms that the Hinterlands existed during the Second War). Northeron has not appeared in recent releases and both share somewhat similar descriptions (forested and mountainous) as well as being described as the homeland to the Wildhammer dwarves.