4711 is the name of a famous Eau de Cologne from Cologne in Germany. It was designed by distiller Peter Heinrich Molanus in 1820. The current bottle in Bremer blue and gold is a classic that was designed in 1839. The recipe is still a secret blend that is matured in oak casks.
The number comes from the house number given to the house of Wilhel Muelhens in Glockengasse during the French occupation in 1796.
It became a registered trademark in 1875.
Source: http://www.4711.com