Arcadian's namesake comes from his father, who came into contact with a member of the Arcadians in the Underdark. However, what most do not know, is why his father was in the Underdark to begin with. Goliaths always strive to gain strength and become better warriors - thus explaining why Goliath tribes change leadership often. Arcadian's father had always heard that the Underdark was a place to be avoided and reckoned with. Hearing that, he of course soon after developed an obsession with the Underdark, and with conquering its creatures.
Arcadian being his son, knowing his namesake and that his father perished there, has inherited his obsession. Not for revenge - but to overcome and be better than his father, and meet the very creatures his name is derived from. Thus, Arcadian is traveling the world, hoping for a chance to get to the Underdark, conquer its domain, and meet his namesake.