Vicarius

Vicarius is a Latin word, meaning substitute or deputy. It is the root and origin of the English word "vicar".

Originally, in ancient Rome, this was an equivalent to the English "vice-" (as in "deputy"), used as part of the title of various officials. Each vicarius was assigned to a specific superior official, after whom his full title was generally completed by a genitive (e.g. vicarius praetoris). At a low level of society, the slave of a slave, possibly hired out to raise money to buy manumission, was a servus vicarius.

Later, in the 290s, the Emperor Diocletian carried out a series of administrative reforms, ushering the period of the Dominate. These reforms also saw the number of Roman provinces increased, and the creation of a new administrative level, the diocese. The dioceses, initially twelve, grouped several provinces, each with its own governor. The dioceses were headed by a vicarius, or, more properly, by a vices agens praefecti praetorio ("deputy of the praetorian prefect"). An exception was the Diocese of Oriens, which was headed by a comes ("count"). In 370 or 381 Egypt and Cyrenaica were detached from the Diocese of the Orient and made a diocese under an official called the Augustal Prefect.