Q9: Where did the Organization’s coat and mark come from?
A: Xemnas remembering his human years.
One year after BbS, Xehanort as well as five other apprentices toss aside their hearts. Then the Nobody Xemnas was born, and the Organization which he creates take a lot of things from his memories as a human. But as Xemnas had two people who he was, Terra and Master Xehanort, he takes from both of their memories.
[picture: Master Xehanort in dark coat]
The coat used by the Organization was something that Master Xehanort originally wore.
[pictures: Terra’s mark, Nobody’s mark]
The Nobody mark used by the Organization is a similar shape to the mark Terra used.
[pictures: Roxas receiving his name, Vanitas and the X-Blade]
Xemnas gives Organization members names with an X in them. This has something to do with Master Xehanort’s interest in the X-Blade.