Man pages matching name mfont_list_family_names in section 3m17n:

mfont_list_family_names.3m17n.en	debian 10 / m17n-docs
mfont_list_family_names.3m17n.en	debian 11 / m17n-docs
mfont_list_family_names.3m17n.en	debian 12 / m17n-docs