The term "Satrap" is the Greek form of Persian Kshtra-pavan, which means "protector of realm" and its Sanskrit equivalent is `Kshatrapa`. The term `Satraps` refers to the subordinate rulers who act as the protector of the realm. The Satrapal system of administration was introduced by the Achaemenian kings in 6th century B.C. Originated in Persia, the Satrapal administration was revived by the Indo-Greeks in India. Satrapal establishment became a regular feature of Indian administration in the Saka-Parthian-Kushana period. There were two grades of the Satrap governor- the Satrap and the Great Satraps. The post of Great Satrap was superior to the Satraps. Epigraphic and numismatics data provides the names of many Satrapal officers who had predominated ancient India. As historical records state, there was a contest among the Satrapal officers, and ultimately four Satrapal houses rose to great prominence. These four Satrapal families were categorised by the historians into two groups for convenience. These were- the Northern Satraps of Taxila and Mathura and the Western Satraps of Maharashtra and Ujjaini.