It has been remarked, that this prince established Saad Ebn Zenki, who had been his governor, lieutenant-general of all his dominions, under the title of atâbek; which signifying Father of the Prince, and being given to the tutors of the Seljûkian princes, became afterwards a title of dignity.
Source: wiktionary
The most powerful office which came to be held by Mamluks was that of atabeg... The function of the atabeg was to act as the tutor and guardian of a young Seljukid prince, and where his ward was the holder of an appanage, the atabeg was in effect a regent with plenary powers.
Source: wiktionary
The Atabeg was watching for this opportunity.
Source: wiktionary
In 1115 Tughtigin took a big step forward by joining a diverse war coalition comprising the atabeg of Aleppo, the powerful Turkish warlord Najm al-Din Ilghazi, and Roger of Salerno, the regent of Antioch.
Source: wiktionary