I would really like to see this engine gain popularity and I think the name is all the stands in the way. But, the clever country code urls are missing the branding point. Brands that stick in people's heads are often completely new words: Kodak, Kleenex, Facebook, Honda. Google and Twitter walk that line where the word exists in English, but is rarely used.
The word should be synonymous with the product -- if there's any kind of punctuation or spelling confusion, it will not spread easily. I should be able to hear the word once, go to a browser, and type it in with no extra explanation. Also, if the url doesn't end in "dot com," most people won't understand or won't see the engine as legitimate.
Google can be made into a verb, so it gains enormous viral marketing power. You can't "DDG" that, you can't "duck" that. And the word can be whimsical, but shouldn't make people feel ridiculous in conversation. E.g. "I'll goosie that." "Quack" is, in my opinion, veering toward "too ridiculous."
In my opinion, these are the qualities to look for:
* Two syllables, with stress on the first (KO-dak, HON-da, GOO-gle, YA-hoo, ZO-ho)
* Either not a word, or a very rarely used word that could be abducted without a struggle
* Not too childish or silly -- could conceivably be found serious conversation
* Easily applicable as a verb or noun, rolls off the tongue in a variety of sentences ("I'll ___ that," "have you checked ___," "I found it on ___")
* Easily spelled once heard
I understand the fears of confusion through total rebranding, but I think there's a great deal more to gain.