According to Name IDs section of https://www.microsoft.com/typography/otspec/name.htm

2 Font Subfamily name. The Font Subfamily name distiguishes the font in a group with the same Font Family name (name ID 1). This is assumed to address style (italic, oblique) and weight (light, bold, black, etc.). A font with no particular differences in weight or style (e.g. medium weight, not italic and fsSelection bit 6 set) should have the string “Regular” stored in this position.
4 Full font name; a combination of strings 1 and 2, or a similar human-readable variant. If string 2 is "Regular", it is sometimes omitted from name ID

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/whats_new.rst if major new feature
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way