Parabellum is from the phrase ‘Si vis pacem, para bellum’ ( if you want peace, prepare for war), which is adapted from a statement found in Roman author Publius Flavius Vegetius Renatus’s tract Dē Rē Mīlitārī.
The sentence was the motto of the Deutsche Waffen und Munitionsfabriken, the German weapons and munitions factory, which developed the 7.65 mm and 9mm parabellum rounds.