Arse - An old term for the fall-side of a block; also called the choke. The word could go back to the Greek orsa, tail.
Boxhaul (also Box Haul) - To wear a ship in a square-rigger, in limited space, sometimes to minimize forward movement. Its origin is uncertain, but in all probability is the same as for Box.
Box - A verb, to name the points of a compass. The term probably evolved in the XVIII century, and, again probably, came from the Spanish bajar, to sail around.
Oakum - Caulking material made of tarred yarn fibers, earlier of flax, the latter also called tow. The origin of the word is Anglo-Saxon, acumba, tow; the Middle English sometimes was ockam.
Spitfire - A small jib, also a storm jib. The origin is obscure, but implies defiance to high winds and heavy seas.
Information is from the book "Origins of Sea Terms" by John G. Rogers
copyright 1985 Mystic Seaport Museum, Inc. and available from BlueJacket.