Nunchuks is more of a short cut for nunchaku which is a weapon made of two sticks (usually of equal length) joined together by a rope or chain. This weapon can be used to strike, wrap around opposing weapon to neutralize them, as well as for choking and locking moves.
Another thought is that is originated from China since there was a time of Chinese migration to the Okinawa island. In China there is a similar weapon known as a two section staff. Unlike the nunchaku, one of the sticks was much shorter and the other longer. With the longer stick being the handle and the shorter stick for hitting.
The ideal length of the sticks of the nunchaku should be able to cover the length of the forearm. The sticks itself is made of hardwood. The traditional rope used to connect the two sticks was made of horse hair. The length of the rope should be slightly longer than the width of the hand.