"Physiocrat" was a term used in France during the French Revolution to describe the economic reformers who encouraged the government to simplify the tax system and remove the mercantilist constraints from the economy. An example of a mercantilist constraint is control on the price of grain which had been imposed to keep the cost of bread low. The physiocrats claimed that this interfered with the natural workings of the market. From that example, you get the idea that a physiocrat is an economic reformer who aims for a freer economy, like the French revolutionary aiming for more liberty and justice.