From BiblePortal Wikipedia

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [1]

Two different authors are frequently quoted by this title.

1. A celebrated canonist who flourished in 1250, and wrote a Commentary on the Five Books of Decretals, printed at Venice in 1588, folio. He is known as Abbas Antiquus.

2. The celebrated Nicholas Tudeschi, the Panormitan, known as Abbas Siculus or Abbas junior. (See Panormitan).

Supplemental From Volume 11:

( Ἀββᾶς ), a Greek term for (1) father, (2) a monk, and (3) an abbot.

(properly Abd-el-Mottalib), the paternal uncle of Mohammed and progenitor of the Mohammedan dynasty of the Abbassides (q.v.), was born at Mecca about A.D. 566. He was but four years the senior of Mohammed, and was still a pagan when the prophet began his public career, and long remained his open enemy. He fought against Mohammed in the battle of Bedr, and was taken prisoner; but as soon as the cause of the prophet seemed to succeed he gave in his adhesion to the new faith, and defended it zealously. When Mecca surrendered to Mohammed, the holy well Zemzem was retained, although a monument of paganism, in deference to Abbas, its keeper. He was the chief mourner at Mohammed's funeral, and his presence and memory were treated with great respect by the caliphs.

The Nuttall Encyclopedia [2]

Uncle of Mahomet, founder of the dynasty of the Abbasides (566-652).