The word "yaqut", via the Syriac arabicized Greek (hyakinthos), means hyacinth (or corundum). It became the name of at least five well-known Muslim schlolars who were slaves that were taken into captivity during the Holy War (jihad) and educated obligatory as Muslims. Two of them became famous. 1.Yaqut al-Mu'tasimi (m. 698/1298) became a librarian and a famed calligrapher. 2.Yaqut al-Rumi al-Hamawi (m. 626/1229), captured as a Christian boy, traveled to many lands. He became also a librarian. Of his numerous works, two should be mentionend, the "Dictionary of learned men", and the "Geographic dictionary".