[My] mama didn't raise no fool. = "Mi mamá no crio a un tonto".
Y puesto que la persona a quien crio mi mamá soy yo, la oración viene a significar que yo no soy tonto.
Y sí, es una expresión.
Lucky you!And @Reina de la Aldea, it's been many a long year, but I'm pretty sure I did hear this sentence now and then while growing up in rural Texas.
It sounds SO much better with no fool. The double negative gives it extra punch. It's more than a statement of fact, it's a bold assertionwouldn't it be more correct, then, to say "Mama didn't raise a fool", instead of "no fool"?