Its origins lie in present-day Southwestern Nigeria, covering the majority of Oyo, Ogun, Osun, Ondo, Ekiti, Kwara, and Lagos states, along with parts of Kogi state and adjacent areas of Benin and Togo, collectively known as Yorubaland (Yoruba: Ilẹ̀ Káàárọ̀-Oòjíire) [coordinates n="7.9465" e="3.3869" z="6"].
The term Ajogun is derived from the phrase "A + Jẹ + Ogun," meaning "That which feeds on trouble."