Quote Originally Posted by lateralus
Hm, Chowder, exactly how much is a fifth? Is it a fifth of a liter? I've always wondered.
Hmm, I know I have heard that before as well, a "fifth." Maybe a 5th of a gallon of booze?

Here, I was partially right...I found this though for ya:

fifth (fĭfth)
n.
-The ordinal number matching the number five in a series.
-One of five equal parts.
-One fifth of a gallon or four fifths of a quart of liquor.