5251977 was a minor planet, so insignificant it only possessed a numerical identifier. Its rotation was so unhurried that its days and nights were as long as several weeks on other worlds. After the Alliance to Restore the Republic suffered a defeat by the Galactic Empire, they left Echo Base on Hoth and constructed a new base on 5251977. This new base was significantly larger than the old one, and included a sizable hangar containing various starfighters, ships such as the Mighty Oak Apocalypse, and a few Dornean gunships. Before the Battle of Endor, Corona Squadron relocated to this base.
The designation for the planetoid, 5251977, comes from the original release date of Star Wars: Episode IV A New Hope. Specifically, it's based on May 25, 1977, or 5/25/1977, as it's written in United States date and time notation.