Webster's Dictionary 
(1): ( n.) A parish priest in the Greek Church.
(2): ( n.) A child's word for father.
A Dictionary of Early Christian Biography 
Papa. See Nestorian Church
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
( Πάππας ), a name originally given to the bishops of the Christian Church, is now the pretended prerogative and sole privilege of the pope, or bishop of Rome. The word signifies no more than Father . Tertullian, speaking indefinitely of any Christian bishop who absolves penitents, gives him the name of Benedictus Papa . Heraclas, bishop of Alexandria, has the same title given him. Jerome gives the title of Papa to Athanasius, Epiphanius, and Paulinus; and, writing often to Augustine, he always inscribes his epistles Beatissimo Papoe Augustino. The name Papa was sometimes given to the inferior clergy, who were called Papa Pisinni, that is, little fathers; in comparison with whom Balsamon calls presbyters Protopapae i.e. chief fathers. The Greek Christians have continued to give the name Papa to their priests. There is at Messina, in Sicily, an ecclesiastical dignitary styled Protopapa, who, besides a jurisdiction over several churches, has a particular reverence paid him by the cathedral; for upon Whitsunday the prebendaries go in procession to the Protopapa's church (called the Catholic), and attend him to the cathedral, where he sings solemn vespers, according to the Greek ritual, and is afterwards waited upon back to his own, church with the same pompous respect. As a title, the word papa appears to have first been used by bishop Siricius in the 4th century; its use became more frequent in the course of the 5th century, and since the 7th century it disappears for all ecclesiastical officers except the bishop of Rome; and Gregory VII expressly claimed it as an exclusive prerogative of the Roman see. (See Pope).