The River Severn, one of the longest rivers in the United Kingdom, has many synonyms that describe its beauty and importance. Some of the synonyms for the River Severn include the Sabrina River, the Hafren River, and the Afon Hafren. The nickname Sabrina was given by the Romans, who believed that the river was the dwelling place of the goddess Sabrina. The Welsh name for the river is Afon Hafren, which means "boundary river." The river flows along the Welsh-English border and therefore marks the boundary between the two countries. In addition, the river is also sometimes referred to as the "King of Rivers" due to its size and significance.