Even in his day Twain, yes his name was Mark Clemens, Twain is shorter, took a lot of flack for the lack of what is now political correctness.
His name was SAM Clemens.
Mark twain is a navigational term meaning 2 fathoms, or 12' of water, the shallowest considered save for navigation. Clemens was a Mississippi river boat captain and he adopted the term for his pen name.
