Complex sentence: In the times of Kievan Rus, the word "gusli" simply referred to a stringed instrument, and eventually became associated with the trapezoidal fourteenth-century "gusli-psaltyry" (which may have originated in Byzantium).
Split into simpler sentences: In the times of Kievan Rus, the word "gusli" simply referred to a stringed instrument. The term was eventually associated with the trapezoidal "gusli-psaltyry" (which may have originated in Byzantium).