- Billy Yank: A nickname for a Union soldier originating in the Confederate states.
- The Boys in Blue: Often in contrast with the Confederate nickname "Butternuts," this was the nickname for the US Army worn blue uniforms.
- Damnyankees: A derogatory term used by Confederates to refer to Union soldiers.
- Federals: A term for Union soldiers or members of the US government as they upheld the federal law.
- Mudsills: A derogatory term for Union soldiers implying that they were inferior manual laborers.
- Roundhead: Refers to the short haircut typically worn by Union soldiers.
Confederate:
- Butternut: A nickname for Confederate soldiers, likely derived from the color of their uniforms.
- Johnny Reb: A southern counterpart of the Union's Billy Yank.
- Rebs: A shortened form of the word "rebels."
- Greybacks: A reference to the Confederate soldiers wearing grey uniforms.
- Secesh: Short for secessionists, the people who broke away from the US.
- Dixie: Nickname for the Confederacy, it may have been inspired by the popular song "Dixie."