A mark was an old term used to describe the depth of a body of water as a ship passed through it. A mark was about 6 feet so mark twain, or two marks, was 12 feet. Unless you meant what was Mark Twain's real name, in which case it was Samuel Langhorne Clemens.
Samuel Langhorne Clemens
The real name of the American author Mark Twain was Samuel Langhorne Clemens (1835 - 1910).
Writing
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Mark twain liked visiting libraries as a youngster.
Mark Twain's real first name was Samuel. He was born Samuel Langhorne Clemens.
Mark Twain's first job was as a typesetter.
November 30th 1835
michael twain
It was Susy Clemens.
Shania Twain
he invented to computer