In Assassin's Creed Origins, Bayek of Siwa is named after the Siwa Oasis in western Egypt. Bayek is a Medjay, a traditional Egyptian protector and law enforcer, whose story takes place during the Ptolemaic period.
The Siwa Oasis is also where the game begins. Its isolated desert setting establishes Bayek’s identity, duties, and relationship with his son Khemu before the main investigation carries him across Egypt.
Origins is set in the first century BCE, during the reign of Cleopatra VII. The game depicts the origins of the Hidden Ones, the organization that later develops into the Assassin Brotherhood seen in other historical periods.
Siwa is one of several Egyptian regions represented in the game. The Faiyum, Alexandria, Memphis, and the Giza area are also important locations, but they are separate from Siwa. “Bayek of Siwa” therefore identifies his place of origin rather than a title for a fictional kingdom.