Answer
Silver dirhams are a type of coin that was used in the Middle East and North Africa during the Middle Ages. They were first minted in the Abbasid Caliphate in the 8th century, and they quickly became the most popular coin in the region. Al-Hajjaj ibn Yusuf was a governor of the Abbasid Caliphate in the 8th century, and he was responsible for changing the design of the silver dirhams.