Kira: If it is repeated as “kira kira” (キラキラ) or written with Yōon (キラッ), it could be the onomatopoeia of the state of shining. (Pulled from Yahoo Answers.) Also kira in Japanese is often used for ‘killer.’
Vasilli: It sounds very similar to Vaseline. And considering how Vasilli game play can be considered banal… Banal Vasilli… does it really have to be explained any further? Cough.
Vasilli for reals: Vasilli, Vasili, Wassili, are related to the Old Greek word Basil which apparently means: royal, kingly. (Yanked from babynamepedia) Now let us assume that the player behind the Vasilli merc is very good and that he or she is constantly getting those kills. Thus a lot of kills, very few deaths, and in online FPS games that usually makes the player ‘kingly.’ I do not think it has been used in decades, but the best kill death ratio used to make you the king of the server.
Now, the above are just speculation. But does it help?