Uncle Tom was a character in the anti-slavery novel Uncle Tom's Cabin, written by Harriet Beecher Stowe in the mid 1800s. In the novel, Uncle Tom is a slave who, due to the debts of his owning family, is sold to a slave trader, and eventually to Simon Legree. After Uncle Tom refuses to whip another slave on the plantation, Legree resolves to crush his spirit and devotion to God. On the verge of giving up and renouncing his faith, Tom has visions of Jesus and Eva, a white girl he befriended earlier in the novel, and remains true to his faith. After encouraging other slaves to escape, he is confronted by Legree who demands Tom tell him where they are. When Tom refuses again, he is beaten to death by Simon Legree.
The name "Uncle Tom" has become a pejorative term used by African Americans to describe a black man who is overly submissive to white people, betraying his black roots. Sometimes it is used to describe a black person who seeks favor or acceptance with white people by way of unnecessary accommodation. It is also used as a pejorative against any black person who chooses to support conservative ideas or Republican Party candidates (notwithstanding that, without Republican support, slavery would not have been outlawed after the Civil War, and neither the Civil Rights Act nor the Voting Rights Act would have passed Congress).
This use has been criticized by others who point out that Uncle Tom was not submissive, but was beaten to death for refusing to submit. They also dislike the term as it suggests a black/white divide that implies interracial communication and friendship is improper.