of the river may derive from a Portuguese transliteration of the name of the Zenaga, also known as the Sanhaja. Alternatively, it could be a combination of the supreme deity in (Rog Sene) and o gal meaning body of water in the Serer language. It is also possible that it derives from the Wolof phrase "Sunuu Gaal," which means "our canoe". History Early and pre-colonial eras Archaeological findings throughout the area indicate that Senegal was inhabited in prehistoric times and has been continuously occupied by various ethnic groups. Some kingdoms were created around the seventh century: Takrur in the ninth century, Namandiru and the Jolof Empire during the 13th and 14th centuries. Eastern Senegal was once part of the Ghana Empire. Islam was introduced through Toucouleur and Soninke contact with the Almoravid dynasty of the Maghreb, who in turn propagated it with the help of the Almoravids and Toucouleur allies. This movement faced resistance from ethnicities of traditional religions, the Serers in particular. In the 13th and 14th centuries, the area came under the influence of the empires to the east; the Jolof Empire of Senegal was also founded during this time. In the Senegambia region, between 1300 and 1900, close to one-third of the population was enslaved, typically as a result of being taken captive in warfare. In the 14th century the Jolof Empire grew more powerful, having united Cayor and the kingdoms of Baol, Siné, Saloum, Waalo, Futa Tooro and Bambouk, or much of present-day West Africa. The empire was a voluntary confederacy of various states rather than being built on military conquest. The empire was founded by Ndiadiane Ndiaye, a part Serer and part Toucouleur, who was able to form a coalition with many ethnicities, but collapsed around 1549 with the defeat and killing of Lele Fouli Fak by Amari Ngone Sobel Fall. Colonial era In the mid-15th century, the Portuguese landed on the Senegal coastline, followed by traders representing other countries, including the French. Various European powers—Portugal, the Netherlands, and Great Britain—competed for trade in the area from the 15th century onward. In 1677, France gained control of what had become a minor departure point in the Atlantic slave trade: the island of Gorée next to modern Dakar, used as a base to purchase slaves from the warring chiefdoms on the mainland. European missionaries introduced Christianity to Senegal and the Casamance in the 19th century. It