What is "kuyaba"

Kuyaba ( Kūyāba) was one of the three centers of the Rus or Saqaliba ( early East Slavs) described in a lost book by Abu Zayd al-Balkhi (dating from ca. 920) and mentioned in works by some of his followers ( Ibn Hawqal, Al-Istakhri, Hudud ul-'alam). The two other centers were Slawiya ( Ṣ(a)lāwiya) (tentatively identified with the land of Ilmen Slavs, see Rus' Khaganate) and Arthaniya ( ’Arṯāniya) (not properly explained).

Soviet historians such as Boris Grekov and Boris Rybakov hypothesized that "Kuyaba" was a mispronunciation of " Kiev". They theorized that Kuyaba had been a union of Slavic tribes in the middle course of the Dnieper River centered on Kiev (now in Ukraine). Kuyaba, Slaviya, and Artaniya later merged to form the state of Kievan Rus', believed to include modern Belarus and Russia. This explanation has been adopted by modern Ukrainian historiography.