Aminata's Children Being Taken Away
The recurring motif of Aminata's children being taken away parallels the very events of Aminata's life. We see history repeating itself as Aminata was also taken away at a very young age from her homeland in Africa.
Appleby's Punishment of Aminata
Appleby's brutal raping of Aminata as a form of punishment is a symbol for dominance. By doing so, Appleby had hoped to assert dominance over Aminata as a reminder that she did not actually have any rights at all and not even the right to visit Chekura.
The Book of Negroes
The titular Book of Negroes itself is a symbol of freedom. It was only by having one's name entered in the Book of Negros that one could escape a life of slavery in America.
Freetown
Ironically, Freetown ends up becoming a symbol for oppression. When the idea of establishing Freetown is first broached, it is envisioned as a safe haven for black people, a symbol of freedom from oppression by the whites.
However, soon after its establishment, Freetown becomes a symbol for oppression as the black people of Freetown are subject to the strict rules of the British.
The Witherspoons
The Witherspoons are a symbol for oppression. Their taking of May against the will of Aminata is reminiscent of the manner in which black slaves were carted away to American by their colonial masters.