Well, for the DC... an average dwarf is at +3 to his fortitude save against poisons, compared to a similar human. And if you consider that dwarves are more inclined towards the martial classes than other folks (and the Good Fortitude saves those bring)... a first level dwarf warrior is going to have a net +5 compared to a first level human commoner. So, definitely a tough poison.
Ingested poisons in the DMG range from DC 11 to DC 18, and the most high end stuff in the DMG is dragon bile, at Contact DC 26. So, if we're talking a high end, lethal poison targeting dwarves? Somewhere in the neighborhood of DC 25, maybe. Its almost always going to get any low-level dwarf, and it will likely get higher level ones. Of course, it'd be expensive as hell - somewhere in the 2,000 gp range, at least. This is premium stuff for assassins - it isn't for your everyday murder. It'd be reserved for tough targets who *have* to be affected.
Now, you could certainly go with lesser (and cheaper) versions - a DC 20 is still going to get most dwarves most of the time, and everyone else even more often. But if you've got an assassin who has the resources... why settle for anything else?
As for a name?
Beardsbane - I mean, its potent enough to get a dwarf.
