Green’s Dictionary of Slang

(US black) to act in a subservient, obsequious manner to whites; thus Uncle Tomming, Uncle Tommer n.

1882		Nat. Police Gaz. (NY) 28 Oct. 3/1: After a frightful experience [...] he dropped right down to the lowest plane, and took in a mob of Uncle Tommers of the very weakest description.
1905		Minneapolis Jrnl (MN) 29 Mar. 11/4: Another Uncle Tommer shows up. There’ more killin’ goin’ on than in ‘he King of the Opium Ring’.
1942		Z.N. Hurston Dust Tracks On a Road (1995) 775: He can’t even Uncle Tom. Not that I complain of ‘Tomming’ if it’s done right.
1947		S. Lewis Kingsblood Royal (2001) 164: Ain’t but one way to handle a white man: uncle-tom him.
1954		(con. 1920s–30s) J.O. Killens Youngblood (1956) 304: You think it’s alright uncle-tomming for white folks?
1969		‘Iceberg Slim’ Pimp 49: It was a wise thing that I had ‘uncled’ on him.
1970		B. Seale Seize the Time 95: Some Uncle Toming bitch or nigger.
1970		Time 31 Aug. 22: Married or not, for sexual reasons or social ones, most women still find it second nature to Uncle-Tom.
1982		(con. 1970) J.M. Del Vecchio 13th Valley (1983) 201: Often when authority came from a black NCO [...] the black foot soldier felt sold-out, bitter, Uncle Tommed.
1994		N. McCall Makes Me Wanna Holler (1995) 305: That’s one of the most racist newspapers in the country, and you down there Uncle Tommin’ for them!?
2000		Guardian Rev. 18 Mar. 3: Louis Armstrong, who seemed to come closer to Uncle Tomming than any other great figure of the music.