Samuel Langhorne Clemens is better known by his pseudonym Mark Twain. Twain is the archaic word for ‘Two’. He chose this name after having spent his youth on the Mississippi riverside where when the leadsman’s line sank to the two–fathom knot, meaning the boat had a safe twelve feet of water beneath it, he called out, “By the mark, twain!”, which in turn signified the depth up to which it was safe to load a boat.
Source: Origin of Twain’s Name
The Adventures of Tom Sawyer was written by Mark Twain. It was published in 1976.