Drakopoulos was an ancient Greek hunter who discovered a way to trap and kill the Greek god Zeus. At some point, he succeeded in summoning and trapping the ruler of Mount Olympus, but since it's apparent that Zeus escaped from it, it's unknown if he survived the encounter. Drakopoulos wrote all his findings in his journal which was recovered and translated into English by the Men of Letters and stored in the Bunker.
The name "Drakopoulos", when loosely translated into English, refers to a dragon's genitalia. However, it's a commonly found Greek surname that actually means the "dragon's son", or "Drakos' son" if "Drakos" is a first name.
After extensive research, Dean finds a diary from a Greek hunter named Drakopoulos that detailed a method of trapping and potentially killing Zeus. The summoning spell involves a bone from one of his worshippers, and "frozen energy from the hand of Zeus" (fulgurite). Zeus can be killed by a wooden stake made from a tree struck by lightning.
Dean goes on to remark the loose English translation of Drakopoulos' name means "dragon penis", which he finds amusing. The group later finishes Drakopoulos' work when Prometheus sacrifices himself to kill Zeus with one of Artemis's arrows, which are capable of killing immortals.