a mischievous and often morally corrupt person
"The captain of Company L refused to recognize us; said we were deserters, and traitors, and scalawags; and when he drew rations for Company L from the commissary, he wouldn't give us any." Jack London, The Road, 1907
"When times are good, the public generally prefers a scalawag. Clinton was the perfect president for the '90s boom years. Warren Harding would have been a great fit with the boom of the '20s. He drank. He played cards. He snuck out of the White House to go to girlie shows." Bill Bonner, The Market Oracle, December 20, 2011
About the Word:
Also spelled scallywag, this term may originally have referred to an animal of very little value. After the Civil War, scalawag came to describe a white Southerner acting in support of reconstruction governments, often in pursuit of private gain; it was used to insult Rhett Butler in Gone With the Wind.
The origin of scalawag is unknown, but one theory suggests there's a link to the Scottish scoloc, a first-born son given to the Church to educate.