E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Sign your Name.
It is not correct to say that the expression signing ones name points to the time when persons could not write. No doubt persons who could not write made their mark in olden times as they do now, but we find over and over again in ancient documents these words: This [grant] is signed with the sign of the cross for its greater assurance (or) greater inviolability, and after the sign follows the name of the donor. (See Rymers Fdera, vol. i. pt. i.)