Since the Gae Bulg was made of bone and had many barbs, it's not unthinkable that some storytellers imagined a bone harpoon when they described this, the "spear of mortal pain and death." Was the Gae Bulg originally a bone harpoon? That is, in some prehistoric setting, did a storyteller find inspiration in a bone harpoon to create the image of the Gae Bulg? That is impossible to say, but it is also unlikely.

Points of origins for these things are usually impossible to define, but that tends not to be how these folklore work. Since Cúchulainn was the most remarkable of heroes, it stood to reason that he would have the most remarkable of weapons. It is easy to imagine that his spear took many forms before being codified in written documents, removed from oral tradition. The image of a bone harpoon may have helped shape the meandering of this motif as it traversed generations, storyteller to storyteller, but "meandering" is the key here since that is mostly what oral tradition does.