1US derogatory, dialect Designating a person regarded as low, cowardly, or contemptible; especially (in the southern United States) designating a northerner (sometimes specifically a New Englander).
From the mid 19th century sometimes with punning reference to the blue uniforms worn by Union soldiers.
2Especially in the names of animals: having a distinctive blue belly.
Mid 17th century; earliest use found in Faithfull Scout. From blue + bellied.