Wikipedia
Black Dutch is a term with several different meanings in United States dialect and slang. It generally refers to racial, ethnic, or cultural roots. Its meaning varies, and such differences are contingent upon time and place. Several varied groups of multiracial people have sometimes been referred to as, or identified as "Black Dutch," most often as a reference to their ancestors.
Black Dutch is an unofficial American ethnic designation. It was commonly used in Pennsylvania among ethnic Germans, some of whom migrated south to Virginia and other points. Separately, it became adopted around 1830 and afterward among certain Southeastern families of mixed-race ancestry, especially those of Cherokee descent. When used in the South, it usually did not imply African admixture, although some families who used the term were of tri-racial descent.