Scalawag is one of those words that we think of as being a very old-fashioned insult–and it is…but it’s not quite as old as some might think.
Meaning “disreputable fellow,” scalawag only dates from 1848. It originated in American union jargon, and though where it came from isn’t quite clear, it’s thought that it may have been borrowed from the Scotch scallag–a farm hand or rustic. Scallag, in turn, is derived from Scalloway, one of the islands with Shetland ponies, which were deemed undersized and worthless–so to call someone a scallag, and then a scalawag, was to insult their worth. During the Civil War, Southererns used the term as an insult against white, Southern-born men who were not Confederates.