The Collaborative International Dictionary of English v.0.48:

Garfish \Gar"fish`\, n. [See Gar, n.] (Zool.)
   (a) A European marine fish (Belone vulgaris); -- called
       also gar, gerrick, greenback, greenbone,
       gorebill, hornfish, longnose, mackerel guide,
       sea needle, and sea pike.
   (b) One of several species of similar fishes of the genus
       Tylosurus, of which one species (T. marinus) is
       common on the Atlantic coast. T. Caribb[ae]us, a very
       large species, and T. crassus, are more southern; --
       called also needlefish. Many of the common names of the
       European garfish are also applied to the American
       species.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Greenback \Green"back"\, n.
   One of the legal tender notes of the United States; a note of
   paper currency of the United States; -- first issued in 1862,
   and having the devices on the back printed with green ink, to
   prevent alterations and counterfeits.
   [1913 Webster]

U.S. Gazetteer (1990):

Greenback, TN (city, FIPS 30880)
  Location: 35.65176 N, 84.17517 W
  Population (1990): 611 (250 housing units)
  Area: 13.3 sq km (land), 0.0 sq km (water)
  Zip code(s): 37742