XmFontListAppendEntry(3) on Linux
The text 14aabaefcc1b, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A font list function that appends an entry to a font list "XmFontListAppendEntry" "font list functions" "XmFontListAppendEntry"