Westeregg was an Erfworld Side led by Blair, who owned the Arkendish. It was part of a Tribe of green skinned men. It was allied with Easteros, another Side of the same Tribe, that was led by the Ruler's sister. This alliance fought against el-Efbaum and Haffaton. The Side was destroyed by Judy Gale, who was brought to Erfworld by the casting of the Summon Perfect Warlord Spell.
Real World References
In this Wizard of Oz themed section of the story, Bell and Blair fill the roles of the Wicked Witches of the East and West, respectively.
By switching the first two letters in Easteros and Westeregg, the names become Westeros (the main continent of The Song of Ice and Fire series of books) and Easter Egg (a hidden feature in a video or program). While this does fit the general naming scheme of Erfworld, it is unlikely to have any further relevance due to the sides' destruction.
Westeregg also resembles "West Egg", a location in the novel The Great Gatsby.