Ivan, I also live in Charleston and have been trying to figure out the connection between my families and the Ferrettes.I have census records back to 1830, but in 1850 found John F. Ferrett, a fruitier, who claimed to be born in Germany ca 1795. He may very well have come from Haiti, as there was a John Ferdinand Ferrette of about the same age who owned a plantation in Saint Domingue. In John's householdare his son Charles, a tailor, and numerous others (including another Charles Ferrett) listed as Mulattoes.
By 1860, Charles was living with one of my German ancestors in Charleston. Charles died in 1863 in Chesterfield Co, SC.He is buried in the family plot belonging to the son of the German family with whom he was living in 1860. Wish I knew more!However, I do have some census and city directory info that I would be glad to email@example.com