In Trevor Noah's memoir "Born a Crime," he reveals that he called his father "Robert" when he was a child because it was the name his mother, Patricia, used for him.
Patricia and Robert, who were from different racial backgrounds, had a secret relationship during apartheid in South Africa. To protect their son from the harsh realities of apartheid, Patricia pretended that Robert was not Trevor's biological father and instead told everyone that Trevor's father was from a different country.
As a result, Trevor grew up believing that his father's name was Robert.