What is "berendei"

The Berendei or Berindei (in Turkish: Berendi, pl. Berendiler; Romanian: Berindei; Ukrainian: Берендеї, Berendeyi; Russian: берендеи, berendei; in Hungarian: berendek; in Polish: Berendejowie) were a medieval Turkic tribe, most likely of Kipchak-Oghuz origin. They were part of the tribal confederation of the "peak caps" or the "black hats" (in Turkic "karakalpak").