It has been morphed into an apathetic cool, when you acknowledge their existence and words with the words, kewl, and move to another topic, leaving whatever was said behind, not caring, not missing out. A word to express your apathy.
Kewl is how some people name 'cool' in slang. Or sometimes how they pronounce cool is like kewl. Cartman from South Park pronounces cool like kewl but in a longer, more annoying name.
Kewl is the swedish word for describing something/someone funny.
Probably copied by random people who thinks it's pronounced 'cool' and then used it as if it meant 'cool'.
Later, people got annoyed of it and made themselves look like shitheads by defining it on Urbandictionary.com. The same people later gave this defination a thumb down because they felt offensed by it.
And even later, this defination got deleted and no one could read it any longer. But by then, no one cared.