PS, Cheng, this is a great Boxer !
As for the weapons on chains...
A few of those weapons are based on real grain threshing equipment, but like you, I suspect the one in question is pure fantasy...
The main use of a chained weapon is that you can crack a person over the top of their shield. It also gives men on horseback a bit more downward reach.
Otherwise it is a rather (self) dangerous weapon... as a teenager, I knocked myself out playing with a pair of nanchuku ('numb chucks' -- and I felt "numb" afterward)...