Invented brand name, suitable for a range of applications.
The name "killy" has only five characters and only two syllables. Two-syllable names are extremely rare and extremely desirable. Established brands using two syllable names include Sony, Gucci and Twitter.
Killy.com is a dot com domain. Dot com domains are the most desirable domain extension in the world, used by famous websites like google.com. A dot com is the first thing people think of when they think of a website.