Is the word fathom used to measure weight?

Answer 1

No. The "fathom" is a unit used in measuring water depth, and is equal to 6 feet (1.83 m). The author Samuel Clemens used the pseudonym "Mark Twain" because it meant two fathoms, or twelve feet, which was sufficient draft depth required for steamboats on the Mississippi River.

The verb fathom (comprehend) derives from this measuring unit and the measuring process. It applies to determining and understanding the cause for an effect. It is often used in the negative, e.g. He could not fathom why the council would deny his request.