Invented brand name, suitable for a range of applications.
The word "killy" contains only five characters and only two syllables. Two-syllable names are highly rare and extremely sought after. Two syllable names are used by established brands like Lego, Kleenex and Sony.
Killy.com is a dot-com domain. Dot com domains are the most prestigious domain extension in the world, used by famous websites like twitter.com. When most people think of a website, they think of a dot-com.