I just realized something...
Many Wing Chun schools of martial arts emphasize that the Bat Jam Dao are taught only after everything else has been accomplished. While it seems a trend in Chinese martial arts to train the unarmed combat before the armed, fighting was often done with weapons, fist-fight when no weapons were present. So did most of the Hu-die-dao or baat-jam-dao users use them without expert training? It seems unlikely that the knowledge of their use should be held as such a secret by a few great masters and their toughest disciples, where river pirates and their seasonal sea-side kin should be the more common users of such blades.
Perhaps we should look to other martial arts that were more widespread? It seems Wing Chun was relatively unknown until more "recently". Hung Ga? They have a set called 子母雙刀... which I take as "
male-female double knife". I have heard of Southern Mantis practitioners using bat jam dao, but I don't know enough about that style to comment.
Maybe the "river-pirates" only had rudimentary training in baat jam dao use? Surely they weren't looking to fight well-armed fighters, their goals was easy loot from easy prey.
Also, perhaps the hu-die-dao itself was more rare and specialized, but there were knives, daggers, and shortswords with the general look of a single-hand hu-die-dao... perhaps those were used like the big bowie knives of the American Southerners... part bushwhacker, part weapon...?
