fifth Look up fifth at Dictionary.com
M.E. fift, from O.E. fifta, from fif "five." Altered 14c. by infl. of fourth. Meaning "fifth part of a gallon of liquor" is first recorded 1938, Amer.Eng. Fifth Avenue (in New York City) has been used figuratively for "elegance, taste" since at least 1858. Fifth column is 1936, from Gen. Emilio Mola's comment during the siege of Madrid during the Spanish Civil War, that he would take the city with his "fifth column" (quinta columna) in the city as well as his four columns of troops outside it. Fifth wheel "superfluous person or thing" first attested 1631.