The name Abdul Al-Hazrad is obviously a clerical error on the part of Theodorus Philetas or (more likely) by Olaus Wormius the Elder who, knowing no Arabic, translated Philetas' Greek version into Latin. Thus the correct rendering of the Necronomicon's author is Abd al-Hazred.
Hazred is not an Arabic word. It probably is a textual corruption from which one might reconstruct the original. Medieval authors often didn't fully understand foreign languages, and had no bilingual dictionaries available. They often made mistakes even in transliterating, according to how they heard proper names pronounced. For example, hashisheen in Arabic became assassinus in Latin and Assassin in English. The Arabic name Ibn Rushd became Averroes in Latin. If Hazred is a similar case, I would speculate that the actual original was Azread, the elative form of the Arabic verb zarada meaning 'to strangle or devour.' Thus the correct name for the Necronomicon's author is probably Abd al-Azrad, translatable as 'the worshiper of the great strangler/great devourer.'