To avoid overlap. The colloquial name "Firebird" is also in use by another open source project. While we don't believe our use of the Firebird name infringed on their trademark, we wanted to be responsive to the concerns of fellow open source developers.
Why has it taken so long?
See - "Will this name be permanent?"
Why did you choose Firebird in the first place?
With the assistance of attorneys we assessed other uses before selecting Firebird and did not consider these uses to be in the same domain as our web browser. It is very difficult to come up with a good name that is not also used by some other company or project, so choosing and verifying the availability of a name is a complicated process that involves many difficult judgment calls.
It's similar to Firebird. It's easy to remember. It sounds good. It's unique. We like it. And we weren't able to find any other project or company even remotely similar to a web browser that uses the same name.
What's a Firefox?
A "Firefox" is another name for the red panda.
Will this name be permanent?
We sure hope so. We've learned a lot about choosing names in the past year (more than we would have liked to). We have been very careful in researching the name to ensure that we will not have any problems down the road. We have begun the process of registering our new trademark with the US Patent and Trademark office.
How was the community consulted?
The project leads were involved. We reviewed community suggestions made on Mozillazine. We included a group of a dozen or so project staff and other interested contributors in this discussion.
What will the logo/icon be?
How will this affect other Mozilla projects?
Having dealt with this issue, we'll be working out a more detailed branding strategy in the coming months. The branding document will be updated accordingly.
Why not call it _____?
We've chosen a name, and, unless there's another web browser called Firefox that we somehow missed, we're sticking with it. We are not looking for other suggestions. Hundreds of options were thoroughly considered and Firefox is the new name.
Is it Firefox or Mozilla Firefox?
The official name is Mozilla Firefox. We will often shorten that to Firefox.
Won't this confuse people?
Yes, but if the WWF can pull it off, so can we. Besides, in six months you'll forget there ever was any other name.
But I hate the new name. It's stupid.
Our editors are trying to figure out whether this is a question. Of course not everyone will like the new name, especially at first. We're confident most people will quickly get used to it. New names have a way of sounding terrible at first. If you're unhappy with the new name, consider trying out the many improvements we've made in the latest release of our browser - we hope that'll make you feel better. After all, what's most important is how the thing works, not what it's called.
-- Steven Garrity, Gervase Markham, Ben Goodger, Bart Decrem et al.