What is "al-waqidi"

Abu `Abdullah Muhammad Ibn ‘Omar Ibn Waqid al-Aslami ( Arabic ) (c. 130 – 207 AH; c. 748 – 822 AD), commonly referred to as al-Waqidi (Arabic: ). His surname is derived from his grandfather's name Waqid and thus he became famous as al-Imam al-Waqidi. Al-Waqidi was an early Muslim historian and biographer of the Islamic prophet Muhammad specializing in his campaigns. Al-Waqidi served as a judge (qadi) for Harun al-Rashid and Al-Ma'mun. His history books are some of the earliest and most detailed history books on Islam.