The current X.org source uses gr instead of el for the Greek layout.
The change took place 19 months ago, according to
in an attempt to introduce consistency in the layout names.
There is currently a discussion at the Greek localisation mailing list,
about this issue, as several users that, either edit directly /etc/xorg.conf or use setxkbmap, found that their keyboard switching instructions are not working anymore.
Original XFree86 used to call the Greek layout gr and in 2001 a patch was submitted to change this to el:
In general, the end-user should not have to deal with the internal names of the keyboard layouts; the desktop environment should provide human readable names. Currently, the Keyboard Indicator in GNOME offers this facility. It reads xorg.xml where it finds “Greece” and presents to the end-user. The same file lists the internal name of the keyboard layout for “Greece” so the change can take place.
Do you manually configure your Linux in order to write Greek?