What exactly are carbon pencils? A recent question on What are the types of charcoal pencils and how do they differ from each other? had an answer that discussed the relationship of charcoal pencils and carbon. It got me doing a little research in an effort to understand the relationship for myself. It actually left me more confused than anything.
An answer in the aforementioned question talked about Wolffs carbon pencil's which at least on that site are described as:

The carbon pencil is the perfect combination of charcoal and graphite.

The name carbon, for a pencil, is misleading to me since I know natural graphite is pure carbon. Should graphite pencils not just be called carbon pencils then?
I wanted to read a little farther into it and found a page discussing different pencil compositions.

Graphite or “lead” pencils:
As you probably know, pencil ‘lead’ contains no actual lead, just graphite, so it is non-toxic and very stable, and graphite is a form of pure carbon.
...
Carbon pencils:
These are usually made of a mixture of clay and lamp black, but are sometimes blended with charcoal or graphite depending on the darkness and manufacturer. They produce a deeper black than graphite pencils, but are smoother than charcoal.

The description of carbon there is inline with the Wolff's pencil but suggests there are other materials that can be used as well.
It is possible the answer is in the question here but if someone more experienced can chime in that would be helpful.
Why are they called carbon pencils if that is basically what graphite pencils are? Is it being used as a manufacturer buzz word?
The carbon the pencil producers refer to is to be understood as an abbreviation for 'amorphous carbon' one of the three most common allotropes of Carbon (i.e. stablilized multiatomic structures of atomic carbon) The other well know allotropes are Graphite and Diamond. If you had a diamond pencil you would also have a pencil made of carbon - however a much harder carbon allotrope. Hence it will not produce any line (at least not on paper). See also the wikipedia artikle.

'Carbon pencils' will contain amorphous carbon along with other ingredients to produce a deeper black without the scratchyness of pure charcoal.