What is the meaning of the idiom underlined in the excerpt?

Read the excerpt below and answer the question. there was a moment, in time, and in this place, when my brother, or my mother, or my father, or my sister, had to convey to me, for example, the danger in which i was standing from the white man standing just behind me, and to convey this with a speed, and in a language, that the white man could not possibly understand, and that, indeed, he cannot understand, until today. he cannot afford to understand it. this understanding would reveal to him too much about himself, and smash that mirror before which he has been frozen for so long. this excerpt from "if black english isn't a language, then tell me, what is? " is significant because -select all that apply- hughes imagines himself as a black slave. hughes uses black english to emphasize his argument. hughes uses a historical example to explain the origins of language. hughes explains the significance that black english holds for white people.