Caernarvon is an unincorporated community in St. Bernard Parish, Louisiana, United States. The name of the community is from a plantation originally located here. The plantation's name is widely believed to be from a similarly named town and castle in Wales. Names of antebellum plantations in the American South were often reflective of European r…Caernarvon is an unincorporated community in St. Bernard Parish, Louisiana, United States. The name of the community is from a plantation originally located here. The plantation's name is widely believed to be from a similarly named town and castle in Wales. Names of antebellum plantations in the American South were often reflective of European roots and aspirations of grandeur; two upriver Mississippi River plantations, Nottoway near White Castle, Louisiana, and Sans Souci near Osceola, Arkansas, are two examples of this tradition.