Greenback is a slang term for US paper dollars. The name is derived from the note’s color. Dollars were called greenbacks because the backs of the notes were printed in green. The term greenback originated in President Lincoln’s administration.
Greenback dollar history
Greenbacks were paper currency issued by the United States during the American Civil War. They were printed in two forms: Demand Notes from 1861–1862 and the United States Notes from 1862–1865. They were legal tender but not backed by gold or silver, only the US government’s credibility.
The government initially issued bonds to raise capital because bankers opposed issuing paper money as it risked bringing the federal government into markets.
The US government agreed to underwrite the currency’s value, and dollars could now be used to pay back public and private debts.