Medicine was far from an exact science in the 1800s. Death was as much a mystery, as was life. For centuries, physicians struggled over trying to define the causes of death. If a person died, and the doctor really just had no clue, or if the cost of autopsy outweighed the benefits, then they would describe the cause of death as a fever, apoplexy, or convulsions, or what could be visibly ascertained. This was especially true for people they considered to aged.
In 1800s, there was the catch-all category of describing the cause of death, as a Visitation of God. This category was used in a more religious time in history than present day. What it really meant was that the death was inexplicable and it was thought that God had decided that it was time for the person to kick the bucket, buy the farm, gone fishing, in other words, die.
Visitation of God later became death of natural causes.
And yes, apparently there was a place near the city of Nassau, named Congo Buta!