Aker is a geographic area within today's Oslo and a former independent municipality in Akershus, Norway. The name originally belonged to a farm which was located near the current Old Aker Church. The church in turn became the source of the name of the parish, the Akershus Fortress, the municipality and the entire county of Akershus, as well as numerous institutions within this area. The name remains in use in two districts of Oslo, Vestre Aker and Nordre Aker.