The generalissimi was a high rank within the Atrisian Empire, often attributed to warlords. Holders of this rank often used a selfsame appellation of "Warlord of the Empire."
It was rumored that this rank, more specifically the selfsame appellation, had been the inspiration for the title of Warlord of the Empire within the Galactic Empire.
Sources
The Imperial Warlords: Despoilers of an Empire: Part 1 on StarWars.com (original link is obsolete)