At the height of the Middle Ages specific quarters were reserved in cities for certain groups, for example craftsmen, creating communities linked by economic interests, legal or social position or religious affiliation. The Jews also lived together, usually near the city markets, since they were primarily active in trade in the Middle Ages. In Frankfurt they lived directly by the cathedral. There were always Christians living among these early Jewish quarters. From the 13th century there were efforts to put Jews in specific quarters, usually on the edge of cities where they were forced to live in strict separation from the rest of the population. This trend was evident throughout Europe in the late Middle Ages and was the result of a number of factors, including tax revenues for the princes and lords who owned the land the Jews lived on, competition with Christian craftsmen and merchants, and above all the influence of the Church. The term "ghetto" came from the word used in Venice to describe the closed Jewish quarter. Frankfurt had a ghetto from 1462, the Judengasse. Most of the ghettoes in Europe were maintained until the French Revolution, which started the process of Jewish emancipation. The term "ghetto" was reintroduced by the Nazis, who used it to describe the quarters that Jews were forced into, particularly in eastern European cities such as Warsaw, and which were part of the programme of genocide.