A derogatory reference to one's social status... esp. to one's status of being poor and/or starving. If you are poor you would "lick the bottom of the pot" for all of the scraps and leftovers to make sure to get the most out of it while if you were living in opulence you would not need "the bottom scraps" and thus those who were poor were pot lickers.

One who is too stupid to know the function of "pot". a generally derogatory word calling someone Stupid