My uncle used to have a pair of these short swords, whose handle was a grip and trigger with the barrel running parallel to the blade. They looked old and he didn't care if they were authentic or not due to the aesthetic, however I'm wondering, have these ever been a thing? They looked to me as if they were late 18th early 19th century weapons, sort of something a pirate would carry.
In 1838, the US Navy commissioned 150 Elgin "Cutlass" Pistols for the South Sea Expedition. More info here
If your uncle had 2 of those, they would be quite valuable.
it's been asked before but wasn't answered in a lot of detail, you might find more info with the term "Pistol Sword"
Can you post a pic, or find a pic of something similar to refer to?
They did exist but never really became popular because gun knives/swords are not efficient at being either a gun or a knife/sword. As a gun the blade adds extra weight in the wrong places which make it unwieldy and less accurate. As a knife/sword the same problem comes out where there is extra weight in the wrong places and depending if you have a pistol like handle or not this will cause even more problems since it would feel awkward and doesn't allow you to make quick wrist movements to maneuver the sword (which is what most people need when they're blocking or changing direction of the blade). In short people found that it was infinitely more effective to just carry a pistol and sword rather than have a device that tried to merge the two. Pirates would not have used something like this since it's a highly customized/specialty weapon that would take a gun/blacksmith to make and they pretty much used whatever common weapons they could get their hands on. Even if they did have access to them they probably would not have used them for the above mentioned reasons.
Edit: The closest most successful adaptation to a gun blade are bayoneted rifles/muskets since they could be used like a spear in close quarters combat. While a bayoneted rifle/musket was inferior to an actual spear (again because of the weight distribution) it was decent enough for the job that needed to be done. As a gun the blade part was small and lightweight so it didn't alter the weight distribution of the gun very much and it was much easier to compensate for this with a rifle compared to a pistol.
