Firebird was actually the database whose name they hijacked when they had access to AOL's legal army.

Also K9Mail is now Thunderbird for Android.

They didn't really hijacked anything. Firebird made sense coming from phoenix. It wasn't a good choice considering the database existed before but it wasn't really an hijack in the sense that both are significantly different product that trademarks wouldn't have clashed. It was just annoying when doing web searches (similarly to gemini the google AI product vs the protocol).

It wasn't that simple. I couldn't find Firebird's original position post but this is close enough.

https://www.mozillazine.org/articles/article3097.html