x-super-keysym

x-super-keysym is a variable defined in `C source code'.
Its value is

nil

Documentation:
Which keys Emacs uses for the super modifier.
This should be one of the symbols `alt', `hyper', `meta', `super'.
For example, `super' means use the Super_L and Super_R keysyms. The
default is nil, which is the same as `super'.