To add to the naval theme heres a few nautical terms
Brig One of the smaller but more versatile warships of the sailing era was the two masted 'brigantine' (French word for 'Bandit'), or 'brig' as it was abbreviated by the Royal Navy. Small, fast, and well-armed for its size, it served as a scout for the bigger ships, patrol vessel, convoy escort, and errand boy for the fleet. In the last case, it would often be used to run mail, fresh provisions, spare parts, and personnel back and forth to England. Admiral Nelson found them very handy to transport prisoners of war. So many were his victories and so great was his success that for a period of time nearly every brig arriving in England had prisoners aboard, and so many were modified as sea going jails for this express purpose. With every ship having at least one or two troublesome crewmen as well as an occasional prisoner of war, it was customary to put him in the ships own "brig" for a spell.
Gung-Ho - Someone enthusiastic about a job, mission, or effort. Usually applied to US Marines and often among themselves as both an insult and a compliment. It is a Chinese phrase meaning, "work together", or "all together", such as when pulling a heavy weight. This was adopted by US Marines stationed in China just before WW II, and then later formalized as the official slogan for Marine Colonel Carlson's Second Marine Raider Battalion.
Bitter End From the old Norse word "bitt" or beam. A pair of posts fixed on the deck of a ship for securing lines. "Bitter" became a term for a single turn of a cable around the bitts, which was usually the very end of the rope. It became applied to a situation when a person was at the last extremity or very end of his resources. A parallel definition comes from the end of a rope that sometimes hangs over the side of a ship and is closest to the ocean. It's very end is "salty" or "bitter" since it often trails in the water.
Bo'sun Variation of 'Boatswain'. Medieval English in origin. 'Boot' (boat) + 'Swain' (Boy, or Servant). A petty officer on a merchant ship having charge of hull maintenance and related
Between the Devil and The Deep Blue Sea - Falling Overboard, and in great danger. The "Devil" is the longest strake, or seam of the ship's bottom. A luckless sailor who fell overboard and submerged in this fashion had little choice or chance, since he was at the very bottom of the ship.
Before the Mast - Signing on a ship's crew as an ordinary seaman on a merchant vessel, or sometimes as an enlisted sailor on a naval ship. It refers to the fact that the ship rapidly narrows towards the bow after the foremost mast, where it is impractical to stow cargo. Quite naturally, especially aboard merchantmen, it is where the regular crew have their sleeping quarters. Officers and passengers had theirs aft. Popularized by Richard Dana's novel, "Two Years Before the Mast"
Ahoy - This was once the dreaded war-cry of the Vikings.
Aloft The old High German word for 'air' was 'luft', which was combined with the French term 'a', meaning 'go to'. thus 'a luft' became 'aloft' in old English. It means 'to go into the air', or 'climb the mast'.
Yankee - Reported to be Dutch in origin. Fishing boats from Holland often fished off of the coast of what is now New England. Indeed, many of the early settlers in New England and New York were Dutch, and so many of them had the common sur-name of 'Jan', the plural form of which was 'Janke'. Due to the peculiarities of Dutch pronunciation, 'J' is commonly sounded as 'Y' to English speakers. It has since become broadly applied to any New Englander, and eventually, to any North American.
Avast Contraction of two French words, 'Haud Vast', meaning to 'hold fast'. In other words, hang on and stop what you're doing.