A slave in the antebellum South could be a “field negro” or a “house negro.” The former worked as a laborer in the fields, the latter worked as a servant in the house, and usually had an easier workload and better working conditions.
However, to work in the house, a slave had to be compliant and cooperative with their slaveowners. Defiant or combative slaves got sent out to the field.
So, a “house negro” is sometimes used as a pejorative to mean someone who has buckled or assimilated to their oppressors to ensure their own advantage.