I just check something because my memory as faults... Firebird was the name of Firefox and the mail client was called something like Mozilla mail or something else.
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).