The distinction of "orbiting another body, not a star directly" seems pretty clear to me, but the idea of something being the naming example and then no longer being in the group definitely has happened before.
The word "henge" comes from Stonehenge, grew to encompass similar structures, and then was codified in a way that actually excludes Stonehenge itself:
> The "henge" portion has given its name to a class of monuments known as henges. Archaeologists define henges as earthworks consisting of a circular banked enclosure with an internal ditch. As often happens in archaeological terminology, this is a holdover from antiquarian use. Because its bank is inside its ditch, Stonehenge is not truly a henge site.
