greyback

noun6

1. •
   (US, informal) A Confederate soldier during the US Civil War (because of the grey uniforms).

   • ...to resist the farther advance of the greybacks. — 1871
2. •
   (old-fashioned) A louse.

   • It is alleged by the defendant that there were scabs and greybacks in it, and that it did not come up to the quality of No. 1 slate as contracted for. — 1886
3. •
   (US, informal) A Confederate States dollar during the US Civil War.
4. •
   (US, historical) A Confederate States dollar.
5. •
   Any of various grey birds.
6. •
   A kind of paperboard with a smooth white surface on one side and a grey surface on the other side.