Nibbana is simply a common word that describes the extinguishment of a flame. Buddha Gotama used this most common word because it was easily understood and approachable to all audiences in order to describe something outside of conditioned reality and technically outside the realm of language. And it is brilliant.
Now what I am going to say is a supposition, because it has to be.
There is the known wrong view often held and propagated in the Thai Forest Tradition of the “undefiled-citta” or the “radiant-mind” and the awful implied “original mind.” This is woefully wrong. Since Buddha Gotama literally said “all citta are anicca.” Citta exist within conditioned reality as a bridge between “bare-potential-awareness” and an object.
“Bare-potential-awareness” without an object lacks both substance and a self. It exists outside of definition in conditioned reality and language. So this wording is inadequate, but I don’t know another better way of articulating it.
“Bare-potential-awareness” cannot be called a citta or mind because “that” is simply a bi-product of union with an object, not its root nature.
When an object comes before “bare-potential-awareness” it craves, attaches and identifies with the object. Whatever the object, except for the “extinguishment element.” The nature of this “bare-potential-awareness” is to always have an object. It bounces from object to object virtually endlessly and without a discernible beginning.
Greed arises for some objects. Hatred arises for other objects. And delusion arises in all objects (except the extinguishment element) due to the FALSE self identification derived from the object.
The “extinguishment element” is the only object that perfectly reflects/mirrors the “bare-potential-awareness” back at it and since “bare-potential-awareness” inherently lacks both substance and a defined self there is an ending of passion for the object and aversion towards the object. The delusion of a self that is inherent in all other objects is absent in the “extinguishment element,” because it is a pure reflection of the “bare-potential-awareness” which naturally lacks a defined self. A permanent and positive feedback loop is then created. Craving for becoming and birth ceases. Dukkha nirodha. A citta ISN’T formed. This “state”(which isn’t a proper description at all) can be called both nicca, and sukha. While attā is technically absent in this it is actually worthy of attā, but such a distinction is unnecessary.
I am painfully aware of the inadequacy of these words…