Rafin : It is one matter to fire at clay marks, but much another to nullify the Nemesis. That's what Namon told, and he told the truth before he went to the gloried way after. Chakotay: He was right. Killing's not easy. Rafin: Risking my own days and nights to drive the Nemesis from our sphere.
That should be as easy as a long sleep. Soldiers often come up with a name for the enemy that's easy to remember, usually quicker to say than their actual name or if they never learn the enemy's name. Sometimes this is a racial or ethnic slur and in some cases becomes such a slur ; sometimes it's a cultural reference, and sometimes refers to appearance.
Doing so is commonly a form of Demonization and has the effect of 'Othering' the enemy, making them seem less human, thus keeping the troops from considering the enemy's humanity , and thus making it easier for the troops to kill them.
For that reason, the practice is often encouraged or at least not discouraged by the troops' superiors while the war's going on. In science fiction or fantasy settings, this is made even easier when the enemy is not the same species as the troops.
In such works this trope may also be the result of the real name being forbidden, or a summons. These designations often find a way into propaganda and slogans used to whip up civilian support for the war effort, and continued use of these terms after the war can indicate a person who lived through the war and either adopted the term as a habit of speech or is having trouble moving past those years.
