The expression "Amesha Spenta" was coined by Zarathustra himself.
In the context of Zoroastrian view of creation, the group of the Amesha Spenta is extended to include Ahura Mazda, represented by Spenta Mainyu.
Ahura Mazda's Spenta Mainyu is the instrument or "active principle" of the act of creation. It is through this Holy Spirit and the Bounteous Force that Ahura Mazda (God) is ingrained in the soul of humans and signifies how the Creator interacts with the world.