It refers originally to slavery times, when black women used to be raped by the white slave owners to produce mixed children. They would usually grow up working in the plantation house and sometimes would receive education, unlike the black slaves who worked outside in the fields.
The mixed children would associate with whites and have privileges the slaves did not.
Now the term refers in a derogatory manner to lighter-skinned people of color, who are sometimes perceived as acting superior to darker-skinned people, and who because of their color, association with whites in what is viewed as a fawning manner, and greater success in life are sometimes resented by those less fortunate.
Since Rasheed got that office job, he is full of himself and acting like a house nigger.