The 9x19, also called the 9mm Luger or the 9mm Parabellum, was adopted by the German Army in 1908 as the cartridge for the famous Luger pistol. It is possible to walk into most stores that carry ammo and ask for 9mm or 9mm Luger or 9x19 and they will know what you mean.
Not to hijack the thread with an ammo discussion, but is there any practical difference between 9 mm Luger and any other 9 mm ammo? In other words, could I use regular 9 mm ammo in my old Luger (if I had one) and use the 9 mm Luger ammo in my Glock (if I had one)? (I’m a .45 ACP guy, myself, so I don’t know.)