This material was originally posted in a private transcript on 3/17/15.
There are two names that can be used to identify higher aspects of the self/Essence. One is a reference to the "higher self" in the sense of all lifetimes. The other is a reference to the collective entity from which one is a part.
These are not static, and are along the same lines as a "nickname," but are often in use specifically for those Personalities/incarnations that open up to these higher selves.
Each of you have two types of "Oversoul," then. One is the collective identity of the Entity to which you belong, while the other is the collective identity represented by the name of a lifetime in which your Essence felt particularly personified.
In your case, your ... Entity is "Willow."