offspring of a white and a mulatto, 1760, from Spanish *terceron, from tercero "a third (person)," from tercio "third," from Latin tertius "a third," from root of tres "three" (see three). So called from being third in descent from a Negro.
Examples from the Web for terceroon
Historical Examples of terceroon
She was of Indian stock at the third remove, daughter of a white and a half-Indian, and so a terceroon as it is called.Royal Highness