The name comes from the Portuguese caldo, 'broth' — a legacy of Portugal's hold on Ziguinchor, which it ceded to France only in the late 1880s.
Fresh fish is gently simmered in a light broth of onion, tomato, garlic and tangy tamarind or lime juice, along with vegetables like cassava, carrot and potato. It's closely associated with the Diola people of Casamance and served ladled over rice.