The word nunchaku comes from nun (ヌン), meaning "twin" and shaku (尺), the approximate length of each arm of the nunchaku

The popular belief is that the nunchaku was originally a short Southeast Asian flail used to thresh rice or soybeans (that is, separate the grain from the husk). It is possible that it was developed in response to the moratorium on edged weaponry under the Satsuma daimyo after invading Okinawa in the 17th century, and that the weapon was most likely conceived and used exclusively for that end, as the configuration of actual flails and bits are unwieldy for use as a weapon. Also, peasant farmers were forbidden conventional weaponry such as arrows or blades so they improvised using only what they had available, farm tools such as the sickle.

However, it seems that mythology surrounding the origins of nunchaku has little historical accuracy. Unlike Okinawan rice flail (utzu), original nunchaku had curved arms, resembling an Okinawan horse bit (muge), which gave rise to the theory that nunchaku was originally a horse bridle.[ Yet another theory asserts that it was adapted from an instrument carried by the village night watch, made of two blocks of wood joined by cord. The night watch would hit the blocks of wood together to attract people's attention and then warn them about fires and other dangers. On the other hand, associating nunchaku and other kobudo weapons with rebellious peasants is probably a part of romantic imagery.

Martial arts on Okinawa were practiced exclusively by aristocracy (kazoku) and "serving nobles" (shizoku (士族)), and commoners (heimin (へいみん)) were prohibited to do so. Furthermore, Okinawan disarmament was never total; nobles were still allowed to carry their swords and members of the royal family and princes were even allowed to have rifles for hunting.

Whatever its origins were, nunchaku was probably not a popular weapon, since there's no known traditional nunchaku kata. This was possibly a result of its lack of efficiency against weapons such as sword and staff.

The nunchaku is claimed to be a very effective close-range weapon by its proponents.[citation needed] When used in combat, the nunchaku provides the obvious advantage of an increase in the reach of one's strike. Somewhat difficult to control, the rope or chain joint of the nunchaku adds the benefit of striking from unexpected angles. Practitioners of the flashier styles contend that the motion of the nunchaku is often found distracting by opponents, who may have trouble keeping up with the nunchaku's rapid movement. In addition, the reach of the nunchaku is often underestimated, even by those experienced with its use. However, when swung, the nunchaku loses between one to two inches in reach from its total length due to the angle between the stick held and the chain.

The original Okinawan techniques involve holding the weapon in a variety of preparatory postures. Once an opponent has moved their weapon or body into close range, the nunchaku is used to strike vital spots, and apply joint locks, chokes and other control techniques. The chain link version of the nunchaku has also been known to be able to fend off enemies with swords or staves.

Gripping the nunchaku is usually a matter of preference. Gripping it close to the chain or rope link increases control but decreases both striking power and reach. A grip further down would have the opposite effect of increasing reach and power while decreasing control and, with the link further out, would also render it susceptible to capture. Unless in expert hands, it is inadvisable to use a nunchaku against a staff or a stick, since disarming is often only a matter of striking at the link and jerking it hard out of the hands of the nunchaku practitioner. It is primarily because of this specific vulnerability of the nunchaku that most styles tend to minimize striking.

Critics of the nunchaku often point to the level of difficulty to control the weapon and question whether the extended reach and unpredictability provide sufficient offensive advantage to offset this disadvantage. The Chinese consider the nunchaku to be the diminutive of the three-sectioned staff, as the dagger is to the sword, and therefore an inferior weapon in comparison
Possession of nunchaku is illegal in a number of countries including Belgium, Germany, Norway, Canada, and Spain. In the United Kingdom it is legal to own for martial arts purposes