Are you impressed now?
The name was chosen in 2020, which you can find out from a good old fashioned google search.
https://wiki.debian.org/DebianTrixie
So a much better explanation of this "hallucination" is that Gemini thinks all "future" Debian releases are called Trixie.
If you asked me after 2020 what Debian 18 would be called, I never would have said Trixie because it was known to already be set for 13.