The title had its origin in the monasteries of Egypt and Syria, spread through the eastern Mediterranean, and soon became accepted generally in all languages as the designation of the head of a monastery. The word is derived from the Aramaic av meaning "father" or abba, meaning "my father". In the Septuagint, it was written as "abbas". At first it was employed as a respectful title for any monk, but it was soon restricted by canon law to certain priestly superiors. At times it was applied to various priests, e.g. at the court of the Frankish monarchy the Abbas palatinus ("of the palace"') and Abbas castrensis ("of the camp") were chaplains to the Merovingian and Carolingian sovereigns’ court and army respectively. The title abbot came into fairly general use in western monastic orders whose members include priests.
An abbot (from Old English abbod, abbad, from Latin abbas (“father”), from Ancient Greek ἀββᾶς (abbas), from Aramaic ܐܒܐ/אבא (’abbā, “father”); confer German Abt; French abbé) is the head and chief governor of a community of monks, called also in the East hegumen or archimandrite. The English version for a female monastic head is abbess.
In Egypt, the first home of monasticism, the jurisdiction of the abbot, or archimandrite, was but loosely defined. Sometimes he ruled over only one community, sometimes over several, each of which had its own abbot as well. Saint John Cassian speaks of an abbot of the Thebaid who had 500 monks under him. By the Rule of St Benedict, which, until the Cluniac reforms, was the norm in the West, the abbot has jurisdiction over only one community. The rule, as was inevitable, was subject to frequent violations; but it was not until the foundation of the Cluniac Order that the idea of a supreme abbot, exercising jurisdiction over all the houses of an order, was definitely recognized.
Monks, as a rule, were laymen, nor at the outset was the abbot any exception. For the reception of the sacraments, and for other religious offices, the abbot and his monks were commanded to attend the nearest church. This rule proved inconvenient when a monastery was situated in a desert or at a distance from a city, and necessity compelled the ordination of some monks. This innovation was not introduced without a struggle, ecclesiastical dignity being regarded as inconsistent with the higher spiritual life, but, before the close of the 5th century, at least in the East, abbots seem almost universally to have become deacons, if not priests. The change spread more slowly in the West, where the office of abbot was commonly filled by laymen till the end of the 7th century. The ecclesiastical leadership exercised by abbots despite their frequent lay status is proved by their attendance and votes at ecclesiastical councils. Thus at the first Council of Constantinople, AD 448, 23 archimandrites or abbots sign, with 30 bishops.