math help, page-61

and likewise the lb.ft in ciggys' example was probably for the same purpose. Although SI is common in physics, American engineers in particular still use imperial units, and they do most of the petroleum engineering around the world hence the units in the question.

But you can have a lot of fun with units. Furlongs per fortnight, ton.fathoms etc.

"A barleycorn was an Anglo-Saxon unit of length. It was originally the length of an actual barleycorn, but became standardized at what is now 8.5mm. The imperial inch measurement was originally called an ynch which was defined as being equal to three barleycorns. Rather nicely, a quarter of a barleycorn is called a poppyseed. Barleycorns are still used today as the unit of shoe sizes. A size 8 is 1 barleycorn larger than a size 7. Originally, the maximum size was set at 13 which was 13 inches exactly, and all other sizes were determined by counting in barleycorns backwards from 13. A size 4, by this system, would be 9 barleycorns less than 13 inches, that is, 10 inches or 25cm. These days sizing varies somewhat from country to country, but barleycorns are still used for shoe sizes in the UK and the USA."

http://listverse.com/2012/03/07/10-bizarre-units-of-measurement/