The minimum working distance usually refers to the distance between the front of the lens to the subject.
Minimum focus distance seems to vary a bit - one end is definitely the subject, whereas the other end might be a lens nodal point, the front of the lens or the film plane.
By the way, some people who access APUG on smaller screens may see incomplete versions of thread titles, so it is always a good idea to repeat the subject of your query in the post itself.