When it comes to pirates, the North African corsairs seem to be the only group that developed a distinct weapon - the nimchas from the 17th and 18th century, which Eric Claude classifies as Algerian. We have multiple examples in European museums with pirate provenance that all share a common type unique to the Barbary coast. This was possible because piracy was a state sponsored activity there and these pirates had all kinds of infrastructure ashore, including the necessary workshops (even if the blades were predominantly imports).
Other pirates who did not enjoy land based support on a similar scale did not really have the resources or ability to focus on developing their own edged weapons, but rather equipped themselves as best as they could, often from a multitude of sources. In the case of the Qasimi pirates, proximity to Oman means Omani weapons would have been the easiest to obtain. It is interesting that in the photographs the Qasimi leaders wear the long, conical hilt swords as these seem like the least suitable for boarding fights from the Omani panoply, with both the older, shorter swords and the Omani/Zanzibari nicmhas looking like much better options, but the photographic evidence is what it is and if they used other weapons in earlier times, we do not have any pictures.
Finally, when it comes to the nimcha like hilt, the Yemeni version seems like a cruder, simplified interpretation of the Oman/Zanzibar one, which leads me to think that it was copied from Oman and adopted in Yemen in the late 19th, early 20th century at the earliest.
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