GREENBACK
bill, note, government note, bank bill, banker's bill, bank note, banknote, Federal Reserve note, greenback
(noun) a piece of paper money (especially one issued by a central bank); “he peeled off five one-thousand-zloty notes”
Source: WordNet® 3.1
Etymology
Noun
greenback (plural greenbacks)
(US) Any bill that is legal tender in the US (originally printed with green and black ink) issued by the Federal Reserve.
The United States dollar.
A unit of American currency issued during the Civil War by the Treasury Department.
Source: Wiktionary
Green"back", n.
Definition: One of the legal tender notes of the United States; -- first
issued in 1862, and having the devices on the back printed with green
ink, to prevent alterations and counterfeits.
Source: Webster’s Unabridged Dictionary 1913 Edition