That's it, Mick - I think it's something to do with using an adverse wind to move forward. My old seafaring chap explained it to me and Patrick O'Brian has Jack Aubrey use it from time to time but it's all a bit to complicated for a sworn landlubber like me. How did I ever come to marry a sailor??
And yes, 9 and 16 are correct.
Just two to go - think Detective stories (possibly) and banquets......

