The word originates from the Latin "classis", which included among its uses the subdivision of the population by wealth (most notably in the constitution of Servius Tullius). In modern usage it was adopted by Defoe (1728) to define "classes of people" in terms of occupation and income. It was widely used by the Physiocratic School (Cantillon, 1755, and Steuart, 1767) and most centrally by Quesnay (1758) to define socio-economic functions. Quesnay's Tableau Oeconomique made farmers the ">classe productive, landlords the classe distributive and merchants the classe sterile.