XmCreateWorkingDialog(3) on Linux
The text 3e8b2a6f0d0b, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
The MessageBox WorkingDialog convenience creation function "XmCreateWorkingDialog" "creation functions" "XmCreateWorkingDialog"