First my mind went to Phoenix (elixir framework), then to X (twitter) before it clicked what this was actually about. Some very overloaded names
Programmers aren't good at checking if the name is taken. We've done this particular one before. Phoenix (Firefox) had to change names because of Phoenix Technologies, then again because of the Borland Firebird Database.
Phoenix was also the name of Mozilla's browser before they changed it to Firefox
I'm hoping they go with phoenix11 #seewhatididthere
The meaning of 'X server' has been well-established for 30+ years.