XmImUnregister(3) on Linux
The text 8dc263567595, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
An input manager function that removes a widget from association with its input manager "XmImUnregister" "input manager functions" "XmImUnregister"