Hi there. Is your surname Joseph? Because your family has a long history in Plaisance. The 1st black elected mayor of Opelousas was John Joseph who was from Plaisance. But your theory has some possiblity to it, but also when the immigrants/refugees from Fort Pitt ( Pennsylvania ) arrived in the Opelousas district around 1781 the area was already called Prairie Plaisance. Many of them settled near Ville Platte. There is a site that talks about & list the " Refugees from Fort Pitt ". And yes many brought slaves with them. The Opelousas courthouse & State Archives in Baton Rouge show the transactions that were done by these individuals.