"people of common descent," a word from the 16th century, from Middle French race, earlier razza "race, breed, lineage, family" (16c.), possibly from Italian razza, of unknown origin (cognate with Spanish and Portuguese raza). Etymologists say no connection with Latin radix "root," though they admit this might have influenced the "tribe, nation" sense.
Original senses in English included "wines with characteristic flavor" (1520), "group of people with common occupation" (c. 1500), and "generation" (1540s). Meaning "tribe, nation, or people regarded as of common stock" is by 1560s. Modern meaning of "one of the great divisions of mankind based on physical peculiarities" is from 1774 (though as OED points out, even among anthropologists there never has been an accepted classification of these).
Just being a Negro doesn't qualify you to understand the race situation any more than being sick makes you an expert on medicine. [Dick Gregory, 1964]
In mid-20c. U.S. music catalogues, "Negro." Klein suggests these derive from Arabic ra's "head, beginning, origin" (compare Hebrew rosh). Old English þeode meant both "race, folk, nation" and "language;" as a verb, geþeodan, it meant "to unite, to join."