Frank, I suspect that the original has been mistranscribed in some way.
Lincoln's buddy Friend S. Rutherford had, in May 1861, applied for a commission as army paymaster. I suspect he, or one of his brothers, is mentioned here. Note that the preceding letter refers to a paymaster appointment.
Friend Smith Rutherford (1820-64) entered service as paymaster, was promoted to colonel of the 97th IL, and died in LA prior to his commission as Brigadier General.