What is the Nickname of the Union?
There nickname was the Yankees.
The nickname for them was contraband. This came out of a little argument between a union officer and a confederate officer. The confederate officer wanted the slaves who were with the union forces and to protect them the union officer told the confederate that they were "contraband." Contraband in war is not returned, so in calling them that the union officer was using military rules to protect them. It was not meant as an insult.