What is "butvydas"

Butvydas (or Pukuveras) ( (Budzivid); also known as Боудивидъ, Liutauras, Пукувер (Pukuvier) Pukuwer or Pucuwerus) (died 1295) was the Grand Duke of Lithuania from 1292 to 1295. His influence was strong during his brother Butigeidis' reign. This led some historians to believe, that they were co-rulers, much like the grandsons Algirdas and Kęstutis. During his short reign Butvydas tried to defend the duchy against the Teutonic Knights; he also attacked Masovia, an ally of the knights. He was a direct ancestor of the Gediminids.