scalawag (n.)

also scallawag, "disreputable fellow," 1848, American English, originally in trade union jargon, of uncertain origin; perhaps an alteration (by influence of wag "habitual joker") of Scottish scallag "farm servant, rustic," itself an alteration of Scalloway, one of the Shetland Islands, with the reference being to little Shetland ponies (an early recorded sense of scalawag was "undersized or worthless animal," 1854). In U.S. history, used from 1862 as a derogatory term for anti-Confederate native white Southerners.