XmFontListCopy(3) on Linux
The text 8ab90c3addb2, 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 copies a font list "XmFontListCopy" "font list functions" "XmFontListCopy"