The planet formerly was an Earth Federation colony that broke away during the Sol Gamma Wave in 2601. It later was conquered by the Republic during the Annexation of the Western Territories in 2743, the Republic's annexation of the 27 independent colony worlds that dominated the space to its galactic west.
The planet rebelled during the Lovejoy Revolution and broke away in May 3073 during the Cessation of the Western Territories. It allied with the other rebelling worlds, forming the Western Confederation of Independent Worlds.
The planet is named for Egeria, a nymph attributed a legendary role in the early history of Rome as a divine consort and counselor of the Sabine second king of Rome, Numa Pompilius, to whom she imparted laws and rituals pertaining to ancient Roman religion. Her name is used as an eponym for a female advisor or counselor.