xdm.options(5) on Linux
The text ca0a0e0f4323, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze) shipped it. The page shows this text now.
configuration options for the X display manager