The soldiers are always going on about x-rays, but I have no idea what they’re talking about. What is an x-ray?
A lot of times, they’ll mention x-rays when I kill an alien, but I think I’ve heard them say it otherwise. I get the feeling that it might just mean “alien”. Why would they call it that?
Answer
It’s common in military parlance to give a short, unambiguous designation to your enemies. Typically the NATO Phonetic Alphabet is used for this type of designation. In situations where your squad may draw from many nationalities, dialects, or ethnicities with different pronunciations of common words, this reduces the chances that a message will be misinterpreted.
For instance, “tango” is used by the military in many situations in place of “enemy target.” Likewise, squads may be given names based on the first letters of the alphabet, such as Alpha/Alfa, Bravo, Charlie, Delta, Echo, and Foxtrot.
The “X” in X-COM stands for “Extraterrestrial” so it follows that when you’re engaging the enemy, you’re fighting “X”es, or “X-Ray” in the phonetic alphabet.
Attribution
Source : Link , Question Author : Invader Skoodge , Answer Author : agent86