system-key-alist

system-key-alist is a variable defined in `C source code'.
Its value is

nil

It is a terminal-local variable; global value is the same.

Documentation:
Alist of system-specific X windows key symbols.
Each element should have the form (N . SYMBOL) where N is the
numeric keysym code (sans the "system-specific" bit 1<<28)
and SYMBOL is its name.

`system-key-alist' has a separate binding for each terminal device.
See Info node `(elisp)Multiple Terminals'.