"dirt-eating," 1850, from Greek *geophagia (according to OED the actual Greek is geotragia), from geo-, comb. form of ge "earth" (see Gaia) + phagein "to eat."
A diseased appetite ... prevails in several parts of Alabama, where they eat clay. I heard various speculations on the origin of this singular propensity, called 'geophagy' in some medical books. [Lyell, "Second Visit to U.S.," 1850]Cf. also pica (n.2).
geophagy ge·oph·a·gy (jē-ŏf'ə-jē) or ge·oph·a·gism (-jĭz'əm) or ge·o·pha·gia (jē'ə-fā'jə)
The eating of earthy substances, such as clay or chalk, that is practiced as a custom or for dietary or subsistence reasons. Also called dirt-eating.