[Jim McDougall]

Its great to have you come in on this Peter!
The 'moplah' type blade does have pretty old ancestry as per many of the references, Elgood notes it as 17-18th c. and it seems "Arts of the Muslim Knight" has these shown (need to find the photos).

It seems one of these (with the Maghrebi style guard system,as pictured below) was captured by Thomas Hopsonn in 1676 from an Algerian corsair. It seems this further supports the Yemeni associations noted by Lofty and Teo on these weapon types, and with these 'Moplah'(?) influenced blades.

In this, there is still a bit of potential for a 'piracy' connection with these two examples, tenuous though it may be. The hilts are clearly far more recent, however the blades resembling the earlier types noted may well have been circulating in these earlier times.

In that case, the regions of North Africa where the Sale' Rovers operated from that city/state in Morocco, as well as the notorious Barbary corsairs from the various Barbary states 17th into 18th c.

It is surprising to know that many of these 'pirates' were actually former European privateers, who moved into these regions in peace time to carry on with their 'trade'. Usually these men converted to Islam and took new names.

As with the often far ranging regions where these groups of 'pirates' operated, along with the complex trade networks which were present through all these areas, the diffusion of weapon forms must have been remarkable.

With that ratiocination, there are of course many possibilities.
Still, by the numbers, the suggestions for probable 'pirate coast' (eastern Arabia) connected to Oman and the 'Barbary Coast' (North Africa) and its connection to Yemen (S. Arabia) seem most plausible.