I just stumbled across this list of company name etymologies on Wikipedia and noticed that Mozilla is also on there. It reads:
from the name of the web browser that preceded Netscape Navigator. When Marc Andreesen, co-founder of Netscape, created a browser to replace the Mosaic browser, it was internally named Mozilla (Mosaic-Killer, Godzilla) by Jamie Zawinski.
Mozilla, the Mosaic-Killer. Funny. (Even though I can't quite say much about the historical accuracy, of course).