Tolkien’s Old English scholarly subject was the poem’s hero Beowulf.
Beowulf is the central figure of the anonymous Old English epic poem of the same name. He is a Geatish warrior who travels to Denmark, defeats the monster Grendel and Grendel’s mother, and later fights a dragon as an aged king.
Tolkien’s professional engagement with Beowulf was extensive. His 1936 lecture, Beowulf: The Monsters and the Critics, argued that the poem deserved serious literary attention and that its monsters were central to its artistic design. The lecture helped establish a more influential modern approach to the poem.
The other names are characters from the same poem: Hrothgar is the Danish king, Wiglaf is Beowulf’s loyal companion in the dragon fight, and Unferth is a warrior at Hrothgar’s court. They are not alternative names for the hero.