buckwheat, n. — Green’s Dictionary of Slang

buckwheat n.

[SE buckwheat, the cereal grain Fagopyrum esculentum, used as cattle-feed in Europe, but cooked for humans in the US; the foodstuff (and thus the term) was popularized by the black child actor William ‘Buckwheat’ Thomas, who appeared in the 1930s Our Gang series of Saturday morning films]

1. (US, also buckwheater) a naïve peasant, a gullible country person.

1866		Beadle’s Monthly Mar. 248/2: The most novel and sometimes very funny experiences are with the aborigines, or, as they are called, the ‘Buckwheats’ .
1881		‘Bill Nye’ Bill Nye and Boomerang 200: Others have sneered at me and called me a horny-handed buckwheater from the rural districts.
1886		Helena Herald (MT) 22 Dec. 1/4: Shakespeare [...] was the son of a buckwheater.
1894		Omaha Dly Bee (NE) 7 Nov. 7/7: I suppose in the end the buchwheaters and pumpkin rollers did as many fortunes out of the ground as the miners.
1900		E.H. Babbitt ‘College Words and Phrases’ in DN II:i 24: buckwheat, n. A greenhorn.
1902		Wichita Dly Eagle (KS) 6 Apr. 19/2: Only a short time ago the early buckwheater [...] fled before the irritable red man.
1907		Worthington Advance (MN) 6 Sept. 1/5: Peter gave chase and [...] his quarry [...] executed many, original, bold and fearless manouvres to elude the wrathy buckwheater.
1942		Berrey & Van den Bark Amer. Thes. Sl. §391.3: Rustic; Bumpkin, buckwheat.
1992		J. Mowry Way Past Cool 32: Washin cars or bussin tables. That all they gonna let a stupid Buckwheat-lookin niggerboy like you do.

2. (US black) a light-complexioned black person.

1968		‘Sl. of Watts’ in Current Sl. III:2 12: Buckwheat, n. A nickname for a friend.
1978		Maledicta II:1+2 (Summer/Winter) 153: Buckwheat [...] Buckwheat was simply the wild wheat bucks ate, a darker, coarser wheat than that cultivated for white people. In time, however, Buckwheat became a general term applied to all blacks, whether bucks or not. Still later, Buckwheat became adopted by urban blacks as a form of familiar greeting: ‘Hey, Buckwheat! Wha’s happenin’?’.
1980		E. Folb Runnin’ Down Some Lines 33: Hey, wha’s goin’ down, Buckwheat?
1991		D. Gaines Teenage Wasteland 220: All night long there are comments about ‘Buckwheat’ and blackness.
2002		‘Touré’ Portable Promised Land (ms.) 151: We Words (My Favorite Things) [...] Sambo. Spade. Spook. Spear chucker. Coon. Darkie. Buck. Buckwheat. Mandingo.