1895, from carbon (paper) + copy (n.). A copy on paper made using carbon paper. The figurative sense is from 1944. Also as a verb, "send a carbon copy (of something)," and as such often abbreviated c.c.
A person or thing that closely resembles another, as in Our grandson is a carbon copy of his dad. Originally this term meant a copy of a document made by using carbon paper. The linguistic transfer to other kinds of duplicate survived the demise of carbon paper (replaced by photocopiers, computer printers, and other more sophisticated devices).
[ c. 1870