Synonyms for Scallywag (same or very similar meaning)
WordNet sense 1 (a white Southerner who supported Reconstruction policies after the American Civil War (usually for self-interest)):
scalawag
WordNet sense 2 (a deceitful and unreliable scoundrel):
knave, rapscallion, rascal, rogue, varlet
WordNet sense 3 (one who is playfully mischievous):
imp, monkey, scamp
From the ODE community, based on WordNet
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