Luger isn't a brand, but rather the casing sizing.

Rather, it's a brand/mark, but not that of the ammunition manufacturer. The (9mm Luger|9x19mm|9mm Parabellum) is the round used by most 9mm handguns, and is manufactured by thousands of companies worldwide. "Luger" is simply the name of the round's designer and the Luger pistol that introduced it.

Parabellum - derived from the latin Si vis pacem, para bellum - "If you seek peace, prepare for war".

Interesting. I'd always assumed that it had to do with the parabolic shape of the bullet, as opposed to earlier flat-nosed designs.