[filoeleven]

Perhaps “value”? The language is data-oriented, and everything you mentioned in [1] except for “symbol” easily falls within that. In Clojure, a symbol always evaluates to a specific value too, so it seems like a good fit.

A Clojure atom is one of the few types that is not immutable, but the way it is updated is pretty strictly enforced by the language, and references to it at any given point in time are still immutable.

I don’t have any insight into your broader question.