In Assassin's Creed Origins, Bayek's title is associated with Siwa, so he is known as Bayek of Siwa.
Bayek is a Medjay, a protector and law officer in ancient Egypt. He begins the game in the Siwa Oasis, where a personal tragedy sends him on a journey across Egypt to confront members of a secretive organization. His investigation helps establish the origins of the Hidden Ones, the precursor to the later Assassin Brotherhood.
Origins is set in the first century BCE, during the reign of Cleopatra VII and the Roman involvement in Egypt. The open world includes Siwa, Alexandria, Memphis, the Nile Delta, and other regions with different landscapes and historical cultures.
Siwa is an oasis in Egypt's Western Desert, far from the Nile Valley. The geographic title distinguishes Bayek from other characters named in the game and reflects the place where his identity and early story are rooted.