The term 'Merchant Off.' is a job description for a Bosn, which is a four-letter word. A Bosn is a sailor or seaman who is responsible for the maintenance and operation of a ship's deck and its associated equipment. They are also responsible for supervising the crew and ensuring that the ship is running safely and efficiently. The Merchant Off. is a higher rank than a Bosn and is responsible for the overall management of the ship, including the cargo, crew, and finances.