Why is the ninth month called September?
Old English abbod "abbot," from Latin abbatem (nominative abbas), from Greek abbas, from Aramaic abba, title of honor, literally "the father, my father," emphatic state of abh "father." The Latin fem. abbatissa is root of abbess.
the superior of a monastic community that follows the Benedictine Rule (Benedictines, Cistercians, Camaldolese, Trappists) and of certain other orders (Premonstratensians, canons regular of the Lateran). The word derives from the Aramaic ab ("father"), or aba ("my father"), which in the Septuagint (the Greek translation of the Old Testament) and in New Testament Greek was written abbas. Early Christian Egyptian monks renowned for age and sanctity were called abbas by their disciples, but, when monasticism became more organized, superiors were called proestos ("he who rules") in the East and the Latin equivalent, praepositus, in the West.