Example of an oak eku 72" long with closeup of round end and ridged spine on top side
Eku (sometimes spelled eiku or ieku) is an ancient weapon of Okinawan kobudō that originated from an oar, approximately 160 cm in length. According to myth, the oar was traditionally adapted for use as a weapon of self-defense by fishermen against foes armed with more conventional weapons. In fact the Japanese had already conquered Okinawa and put their old officers to work teaching the commons some weaponry in order to put them first in line against a possible Chinese invasion. However, since quality weapons were expensive, the civilians had to use what equipment they had. The Ryuku oar, in Okinawa "Eku" or "Eiku", came to represent the naginata. Naginata means "Blade on staff" which is exactly what it is. The Jo stick was used primarily against swords and the Bo staff against spears.
Usually before learning eiku properly, one has to master the bo. The eiku has a displaced center of gravity and is heavier than the bo, and is thus considered more difficult to master. Because of its weight, eku techniques often capitalized on the momentum of large circular attacks. The Eku was used in the Asian movie Bruka Hindiu, where it was the focus of a mysterious power.