Answer:
Caboceers are the native African chiefs that the European Slave traders pick to work with them.
So, the European Slave traders Gave Caboceers a great sum amount of wealth to help them acquire African Slaves. (so they don't have to get their hands dirty)
Caboceers will order the members of their tribes to capture other African people from weaker/smaller tribes and Give those captured to the European. Compared to modern day business, the role of Caboceers probably similar to the role of material supplier.