As a young under-belt belt, I used to twirl them chucks. Got pretty good at it, too. I had a smaller pair given to me by an Okinawan, hard wood, very fast. I had all the moves, even the sound of the whir through the air was impressive. One time I conked myself right behind the ear. Thin skin there, split it wide open. Bled all over the place, couldn't stem the flow. It was a serious mess. Off to the E.R.
Nunchaku were not well known back in 72, I tried to explain them to the Doc as he stitched me up. He said, "So, let me get this straight, you hit yourself behind the ear with a stick....that's attached to another stick with a string....that used to be used to flail rice?" "Yes, sir" I said.
He called over another Doc and told him the story, he also found it amusing. Then a nurse, she found it humorous, too.
When I left he had written down how to care for the wound. Followed by...."Don't hit yourself in the head with any more sticks."
I bought a set of nunchaku at a flea market in Denver about that same timeframe. I think that's the only correct place to buy such things, really, along with fake IDs that no doorman will accept and ninja stars. Tried them for a few days, got bored, gave them to a friend who was a part-time boxer and had very good hand-eye coordination. He was very good very quickly with them. Then hit himself square in the forehead and knocked himself out cold. I don't know what became of them after that.
Our style of martial arts doesn't use nunchaku. We use bo, sai, and tonfa (we call them tuifa). I am getting involved in a new kobudo system which uses more traditional Okinawan weapons, such as tichu, eku (oar), yari, sansetsukon (three-section staff) and others. I'm not that coordinated with weapons, but they make a good counterpoint to empty-hand training, and the underlying methods of power generation and extension are similar.
One thing I am learning is that most traditional weapons are used in exactly the manner that it would appear you would used them - the obvious use of a nunchaku is to flail. However, it is also clear that the originators of the various weapons styles spent a lot of time thinking about them and how else they could be used, and testing how effective they might be used in other capacities. Things like using a nunchaku to trap may be non-obvious, but they can be quite effective as a control mechanism when applied to a wrist or a weapon. Often used less for a 'fight' and more for 'control techniques' such as a law enforcement officer (or village drunk patrol) might use as non-lethal force.
Quite a few traditional weapons, it seems, were adapted later to use as non-lethal restraint and control devices in Japan and Okinawa. In such a manner, I see no reason why the nunchaku would not be excellent as a restraint and a control. In the USMC, we military police used to refer to such things as 'come alongs'. For example, a police baton or nightstick is for beating people over the head with - and it will split a skull quite readily. However, grasped in the middle and passed between the legs from behind, then turned to block forward motion of those legs, combined with a grasping of the collar and leaning the arrestee forward turns it into a very nice frog march tool.
Military Police Protection in Southeast Asia
Some might say "You can't use a nightstick like that!" But we could, and did. A lot more often than hitting them on the noggin, for what it's worth.
So yeah, nunchaku as a trapping weapon? Absolutely. Why not?