All of this invention of various terms for fractions of Black ancestry is based on the silly idea that any "Black Blood" at all makes you Black. This was the rationalization the southern slave owners needed to (often personally) breed generations of slaves that looked much like themselves and the rest of their family, but still be subjugated, sold, murdered, and so forth on the owner's whims.

It was (and still is) silly because EVERYONE has Black ancestry!