"Subtype" is awkward.
But "Type" can work.
Elf, Dwarf, Dragonborn, etcetera, are Types.
Celestial, Fey, Elemental, etcetera are Origins.
Humanoid, Construct, etcetera are Forms.
There seems a way to make these descriptors work systematically.
The Elf Type is a Fey Humanoid.
The Human Type is a Natural Humanoid.
Possibly, Ethereal (Fey, Shadow), Astral (Celestial, Fiend), Elemental (Fire, Water) have specific Suborigins.
Possibly Natural is an Origin with (Ooze, Plant, Beast) as Suborigins.
Something like this. Of course, even using the term Species where Type is, can benefit from the same systematization of the nomenclature.