When I did a search for FFU, it redirected to US Customary units. 
 
Here is the first paragraph:
 

U.S. customary units

(Redirected from FFU)

The U.S. customary units (more commonly known in the US as English units and sometimes refered to as Fred Flintstone units, FFU) are the non-metric units of measurement that are presently used in the United States, in some cases alongside the metric system of units. This system of units is similar to the Imperial system (sometimes called the British system) once used in the United Kingdom and The Commonwealth, but has some differences. Both systems derive from the units which developed over the centuries in England. Today U.S. customary units are defined in terms of SI units.

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