Funny story: The official definitions of Standard and Imperial measures are all backed against the Metric system. (1 foot = 30.68cm)

Funnier story: The Metric system was originally based on 1/10,000,000th of the poorly-measured distance between the North Pole and the Equator, along the line between Dunkirk and Barcelona. After 6 years of improper measuring, and poor correction for the Earth's oblateness, they came up with the meter. They then based all the measures on the meter. (Except time, which is hard to measure without outright saying, "This measure of time was chosen at complete random")

The meter was later redefined as 1/3,000,000th the distance light travels in one second, but it was mysteriously unchanged in actual length. Because in the 1980s, we couldn't observe, accurately, how far light traveled in 1/3,000,000th of a second. So, Imperial and SAE are arbitrary systems based on an arbitrary system. (Arguably, based, itself, on an arbitrary system, since seconds have been around, as the length of time we recognize as a second, long before the definition regarding radioactive decay came about)