Convert from mark twain to rood

Unit Definition (mark twain)
The mark twain or twain is an old word for the number two, derived from the Anglo-Saxon twegen. The American author Samuel Clemens (1835-1910), who had been a riverboat pilot on the Mississippi in his youth, took his literary name from a traditional riverboat phrase "mark twain", meaning "exactly two" fathoms of water. This was the minimum depth needed for the boats to operate safely without running aground.

Unit Definition (rood)
The rood is an old unit of distance, used in several ways. Rood (or roede) is an old Dutch word meaning a rod or pole. So the rood is in some cases another name for a rod. But in old England and Scotland the rood was often longer than a "modern" rod of 16.5 feet; sometimes it was 20 feet, 21 feet, or even 24 feet. In Afrikaans-speaking South Africa, the rood was a standardized measure equal to 12 Cape feet, which is 12.396 English feet or 3.7783 meters.