Uncle Tom is a derogatory name applied to blacks who curry favor with whites usually against the interests of other Blacks. It was first used in connection with a character in the book Uncle Tom's Cabin written by Harriet Beecher Stowe. There has already been a discussion about Blacks who disguised their true feelings toward whites to survive (See Annotation 14). After slavery, as Black Nationalism evolved, acting like an Uncle Tom was largely considered an act of betrayal. In the period when Malcolm was growing up, "Tomming" was also a con, a way in which to get extra tips from whites to supplement low wages -- EB
See for example, Kelley, The Riddle of the Zoot Suit.