Definition of blue-bellied in English:

blue-bellied

Pronunciation /ˌbluːˈbɛlɪd/

adjective

  • 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.

Origin

Mid 17th century; earliest use found in Faithfull Scout. From blue + bellied.