SSID (Service Set Identification)
From DD-WRT Wiki
Service Set Identification
You can choose to broadcast it on an AP or not. A client needs to know this ID to associate with an AP.
On the current implementation of DD-WRT (23sp1) special characters that seem to work with windows are not supported and refuse to be configured and fail to connect. Example: Unsupported Characters in SSID "¡Bienvenidos! AMPM"
While the setting from shell nvram set wl_ssid="¡Bienvenidos! AMPM" seems to configure this id i was not able to verify that this is sufficient and for some reason a reset of the WRT54G cause the SSID to be reset to the previous supported choice.