1432, as a noun, "bishop having oversight of other bishops," from L.L. metropolitanus, from Gk. metropolis "mother city" (from which others have been colonized), from meter "mother" + polis "city" (see policy (1)). In Gk., "parent state of a colony;" later, "see of a metropolitan bishop." In the West, the position now roughly corresponds to archbishop, but in the Gk. church it ranks above it. In Eng., the adj. sense of "belonging to an ecclesiastical metropolis" is from 1548; that of "belonging to a chief or capital city" is from 1555. In ref. to underground city railways, it is attested from 1867.