What is a "Parabellum Pistol"???

[sheepherder]

I was looking for info on proof marks on a revolver I just purchased, and found a couple of .PDF pages taken from The Blue Book Of Gun Values...

https://store.bluebookinc.com/Home/Default.aspx

https://store.bluebookinc.com/Info/P...Proofmarks.pdf

This one is at PIA and seems to be somewhat older -

http://www.phoenixinvestmentarms.com...Proofmarks.pdf

Here's a screenshot of one example of which I am confused...[pic below]...

"since 1891" indicates that they started putting this proof on "parabellum pistols" starting in 1891...before there was a "Luger"...

So...just what is a "Parabellum Pistol"???