mossback (n.)

"extreme conservative, one attached to antiquated notions," 1874, American English, used especially of poor rural whites; earlier (1872) in reference to those from the Carolinas who had hid out to avoid service in the Confederate army (and would have stayed out "till the moss grew on their backs"); from moss + back (n.). The same image is behind the use of the word in angling for "a large old bass or other fish" (by 1889).