Timbuktu was founded by the Tuareg Imashagan or Kel Tamasheq in the 11th century. The Kel Tamasheq roamed the desert during the rainy season in search of grazing lands for their herds and camels. During the dry season, however, they camped a few miles from the Niger river in search of water and grass for their live stock.
Whenever the desert [became] green, the Turareg [left] their heavy goods with an old Tamasheq [woman] called Tin Abutut who shortly thereafter [operated] a warehouse or a depot for commercial goods transiting from the desert. The city of Timbuktu has taken its name from this famous black lady.
Source: Timbuktu Heritage