Here is the whole story from my end. The estate settlement of my gt gt grandfather Peter Herbert in 1825 in Madison Co. AL, lists his children, among whom is a son Hernando Cortez Herbert. This son was my great grandfather, who, as an adult, called himself "F.C." Herbert, or Fernando Cortez Herbert. But I know his mother Rebecca called him Cortez Herbert. I have not found the origin of this name. I did find a Cortez listed in the Charleston, SC Census, and one in Hampton, VA. But so far I cannot make a connection by marriage.
My grandfather named his son Fernando Cortez. Herbert, born in b. 9 Oct 1862, Hardin Co. TN, d. 20 Mar 1946 in Los Angeles Co.
Hope this helps.