Vatican City
The name was first used in the Lateran Treaty, signed on 11 February 1929, which established the modern city-state. The name is taken from Vatican Hill, the geographic location of the state. "Vatican" is derived from the name of an Etruscan settlement, "Vatica" or "Vaticum" meaning garden, located in the general area the Romans called "vaticanus ager", "Vatican territory".
First Vatican Council
The First Vatican Council () was convoked by Pope Pius IX on 29 June 1868, after a period of planning and preparation that began on 6 December 1864. This, the twentieth ecumenical council of the Catholic Church, held three centuries after the Council of Trent, opened on 8 December 1869 and adjourned on 20 October 1870. Unlike the five earlier general councils held in Rome, which met in the Lateran Basilica and are known as Lateran councils, it met in the Vatican Basilica, hence its name. Its best-known decision is its definition of papal infallibility.