Means "righteousness of religion" from Arabic صلاح (salah)
"righteousness" combined with دين (din)
"religion, faith". A famous bearer of this name was the sultan Salah al-Din Yusuf Ibn Ayyub, known in the western world as Saladin, the founder of the Ayyubid dynasty in Egypt in the 12th century. He recaptured Jerusalem from the crusaders and repelled the invaders of the Third Crusade. Salah al-Din was an honourific; his birth name was Yusuf.