Leenia and John,
As one who keeps sheep, and whose fence is currently down because of my neighbor's evil cows, I must disagree with the cavalier equation of shepherd and cowherd. Sheep good;cows bad.
Regarding Greenberg's theory about the 12 sons of Jacob, I would remind you of Occam's razor. (If some old records say Pennsylvania was named for William Penn, and if no old records give any other derivation of the name, then maybe, just maybe, Pennsylvania is named for...)
In any case, the names of the twelve sons of Jacob do not quite correspond to the names of the tribal areas, which is pretty hard to explain if the sons were invented based on the areas.
Kent