"building in Washington, D.C., where U.S. Congress meets," 1793 (in writings of Thomas Jefferson), from Latin Capitolium, name of the temple of Jupiter Optimus Maximus, protector of the city, on the Capitoline Hill in ancient Rome. Used earlier of Virginia state houses (1699). Its use in American public architecture deliberately evokes Roman republican imagery. With reference to the Roman citadel, Capitol is recorded in English from late 14c., via Old North French capitolie. Relationship of Capitoline to capital (adj.) is likely but not certain.
updated on October 10, 2017