"This African banco term which refers to such "earthen construction practices" came from Manding, a widespread language group in West Africa."
The Manding languages are a fairly mutually intelligible group of dialects or languages in West Africa, belonging to the Mande languages.
Their best-known members are Bambara (the most widely spoken language in Mali), Mandinka (the main language of Gambia), Maninka (or Malinké, a major language of Guinea), and Dioula (Dyula or Jula) (an important language of the northern Côte d'Ivoire and western Burkina Faso).
When the Smith family went on a safari to Africa they stopped at a banco building and were intrigued to discover a casino.
When the tourists were visiting a group of natives in their village, the car that the foreign visitors were using, broke down and so they had to spend the night in a banko structure until the vehicle could be replaced the next day.