Born in 1921, Serigne Mouhamadou Moustapha Mbacké Fallilou, better known as Serigne Modou Bousso Dieng, is one of those prominent but discreet figures of Mouridism. The eldest son of Serigne Fallou Mbacké, he is the namesake of the first caliph of the Mourides, Sheikh Mouhamadou Moustapha Mbacké, who personally educated him and taught him the precepts of Islam as well as other Islamic sciences. He spent the first sixteen years of his life with his uncle, before returning to his father's side in 1937 with a solid knowledge base.

Bousso Dieng's son was close to his father, Serigne Fallou Mbacké, for whom he held a deep respect and unparalleled esteem. A key figure during the Caliphate of Sheikh Mohamadou Fadel (1945-1968), he worked unreservedly to promote Islam and Mouridism, the path founded by his revered grandfather, Sheikh Ahmadou Bamba.

In 1971, three years after Serigne Fallou Mbacké was called to God, Serigne Modou Bousso, the newly appointed caliph of Ndindi, decided to make his father's birthday a Magal celebrated in Touba. This is how the Magal of Kazu Rajab was born. More than fifty years later, the event has taken on a popular dimension and is included in the calendar of religious events in Senegal.

Continuing his father's work, Serigne Modou Bousso resolutely committed himself to the development of the villages founded by the latter. Thus, Ndindi, Touba Bogo, Aliya have experienced rapid development with: the construction of health centers, the paving of roads, electrification, drilling, the promotion of modern agriculture, the construction of the Serigne Fallou Residences, etc.

He died in 2000, as he had lived: discreetly.