The attack day on Pearl Harbor doesn't have a name. The days atomic bombs dropped on Hiroshima and Nagasaki don't have names.
I think, generally, people try to think of positive things when naming a day, like a famous person's birthday:
Martin Luther King Day, January 15
Lincoln's birthday (aka President's Day), Feb. 12
Washington's birthday, Feb. 22
Christ-mas, Dec. 25
I've always thought "9/11" is an appropriate name because the numbers, "11," remind me in appearance, physically, of the two towers.
Teri Anne