It comes from a friend of a friend that had a talent for making up words. I know there were others, but the one I remember and still use is "greebly".
Now, I've only heard the word, so the spelling might be incorrect, but that has to be close.
There are a number of things that make "greebly" the greatest made-up word. First of all, you can pretty much "get" the definition just from hearing it. It's not really onomatopoeic, but it kind of sounds like its definition.
Greebly — gross; dirty; icky; disgusting
The second best thing about this word is it's versatility. It's an adjective, of course.
"My keyboard is completely greebly."
BUT. It's also a noun.
"My keyboard is fully of little greeblies."
I love it. It's a great word that is the perfect in so many situations. Make it part of your vocabulary. It's fun!