The Assassin organization before it became the Brotherhood in Assassin's Creed Origins was called the Hidden Ones.
Origins presents the Hidden Ones as an organization founded by Bayek and Aya in the first century BCE. Its members oppose the Order of Ancients, a secretive group seeking political and social control through powerful positions across the ancient world.
The Hidden Ones use covert methods, hidden blades, distinctive symbols, and a creed centered on protecting people from oppression. Their historical development provides the series' fictional explanation for how the later Assassin Brotherhood emerges.
The Order of Ancients is their principal enemy in Origins, not an earlier name for the Assassins. The word “Brotherhood” becomes more strongly associated with the organization in later historical periods, including the Levantine group active during Altaïr's era.