race (n.1)

late Old English, also rase, "a narrative, an account;" c. 1300, "an act of swift running, a hurried attack," also "a course of life or conduct, a swift current;" from Old Norse rās "a running, a rush (of water)," cognate with Old English ræs "a running, a rush, a leap, jump; a storming, an attack;" or else a survival of the Old English word with spelling and pronunciation influenced by the Old Norse noun and the verb. The Norse and Old English words are from Proto-Germanic *res- (source also of Middle Dutch rasen "to rave, rage," German rasen, Old English raesettan "to rage" (of fire)), from a variant form of PIE *ers- (1) "be in motion" (see err).

Originally a northern word, it became general in English c. 1550. Earlier used more broadly, of any course which has to be run, passed over, or gone through, such as the course of time or events or a life, the track of the sun or moon across the sky. Meaning "contest of speed; competitive trial in running, riding, etc. against rivals" is from 1510s. For the sense of "artificial stream leading water to a mill, etc.," see race (n.3). Meaning "electoral contest for public office" is by 1855.

1560s, "people descended from a common ancestor, class of persons allied by common ancestry," from Middle French race, earlier razza "race, breed, lineage, family" (16c.), possibly from Italian razza, which is of unknown origin (cognate with Spanish and Portuguese raza). Etymologists say it has no connection with Latin radix "root," though they admit this might have influenced the "tribe, nation" sense, and race was a 15c. form of radix in Middle English (via Old French räiz,räis). Klein suggests the words derive from Arabic ra's "head, beginning, origin" (compare Hebrew rosh).  

Original senses in English included "wines with characteristic flavor" (1520), "group of people with common occupation" (c. 1500), and "generation" (1540s). The meaning developed via the sense of "tribe, nation, or people regarded as of common stock" to "an ethnical stock, one of the great divisions of mankind having in common certain physical peculiarities" by 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, it means "Negro." Old English þeode meant both "race, folk, nation" and "language;" as a verb, geþeodan meant "to unite, to join."

c. 1200, rasen "to rush," from a Scandinavian source akin to the source of race (n.1), reinforced by the noun in English and by Old English cognate ræsan "to rush headlong, hasten, enter rashly." Meaning "run swiftly" is from 1757. Meaning "run in competition against" is from 1809. Transitive sense of "cause to run" is from 1860. In reference to an engine, etc., "run with uncontrolled speed," from 1862. Related: Raced; racing.

c. 1300, "strong current of water," a specific sense of race (n.1), which then denoted any forward movement or swift running, from Old Norse ras in its sense of "a rushing of water." Via Norman French the word entered French as ras, which might have given English race its specialized meaning of "channel of a stream" (especially an artificial one, to a mill, etc.), which is recorded in English from 1560s.