What name does Assassin's Creed Origins give to the first organized Assassin group?

Assassin's Creed Origins calls the first organized Assassin group the Hidden Ones.

Bayek of Siwa and Aya establish the Hidden Ones after confronting the Order of Ancients in ancient Egypt. The group provides a formal structure for people who oppose political tyranny and work from the shadows.

Origins is set mainly in the first century BCE, during the final years of Ptolemaic Egypt. Bayek is a Medjay, while Aya becomes a central founder and later operates in Rome. Their actions create traditions that later define the Assassin Brotherhood.

The Order of Ancients is not the same organization. It is the secretive power network opposed by Bayek and Aya and is presented as a precursor to the later Templar Order. The Hidden Ones themselves are the historical foundation of the Assassins in the series' fictional chronology.