Complex sentence: Einar is a given name deriving from the Old Norse name Einarr, which according to Guðbrandur Vigfússon is directly connected with the concept of the einherjar, undead warriors from Norse mythology.
Split into simpler sentences: Einar is a given name deriving from the Old Norse name Einarr. According to Guðbrandur Vigfússon, name Old Norse name "Einarr" is directly connected with the concept of the einherjar, undead warriors from Norse mythology.