Naming computer programs

Why do people have to name computer programs or web services with ordinary words?

I'm referring to things like Ubuntu and Android, and one I heard of just today, a social networking thing called Diaspora.

If you are looking for web sites related to ubuntu, or androids, the search engines spew out many totally irrelevant posts.

Computer programs or web sites with unique made-up names have less danger of ambiguity and confusion, like Linux, Facebook, Orkut and the like. Ok, "twitter" is a word, but it's not one that people would really want to look up other than the web site.